Top Layer Research Articles

Study on the Influence of Contact Surface Characteristics on Strength and Fracture Evolution of Layered Cemented Backfill (LCB)

The stability of backfill plays a crucial role in the process of mine operation. In this study, author combined indoor experiments, surface fitting, numerical simulation, and theoretical derivation to investigate how the filling times (FTs), cement tailings ratio (CTR), and minimum CTR filling position (MCFP) affect the uniaxial compressive strength (UCS) and fracture evolution behavior of LCB. The findings demonstrate that an augmentation in FTs reduces the UCS of LCB. Moreover, the highest strength ratio resulting from diverse MCFP amounts to 2.25 times. When once filling, backfill sustain damage as a result of cracks penetrating, whereas LCB that are filled multiple times first encounter damage at the layered contact surface, followed by the gradual spread of cracks until penetrate the LCB. Through an interactive regression model, it is evident that FTs, CTR, and MCFP significantly affect the UCS. Additionally, the interaction between CTR and MCFP has a considerable impact on the UCS. Based on numerical simulation, an increase in FTs results in a wider large displacement area generated by the backfill, leading to greater horizontal and vertical displacement. The MCFP has a significant impact on the lateral displacement and maximum stress of the backfill. Theoretical derivation verifies that MCFP at the top or middle layer results in an increase in the UCS, which is consistent with the experimental findings and numerical simulation. This paper elaborates on the mechanical mechanism behind the interaction between CTR and MCFP. These findings can provide a foundation for assessing the durability and stability of LCB in subsequent stages.

On nonlinear dynamic analysis of hyperbolic tangent FG-GPL-reinforced shallow spherical cap under supersonic flow

On nonlinear dynamic analysis of hyperbolic tangent FG-GPL-reinforced shallow spherical cap under supersonic flow

Species richness and dominant functional groups enhance aboveground biomass, with no effect on belowground biomass in Qinghai-Tibet Plateau's grasslands

Understanding the role of plant diversity in maintaining grassland ecosystem functioning is of great importance in ecological research. Despite decades of research, ecologists have struggled to understand the biodiversity-ecosystem functioning relationships and how the dominance of plant functional groups impacts ecosystem function. In attempting to understand (i) the temporal patterns of above- and below-ground biomass (AGB and BGB) and species richness, (ii) whether species richness is consistently associated with AGB and BGB, and (iii) the relative contributions of plant functional groups (forb, grass, legume, and sedge) in stabilizing ecosystem function, we used biomass productivity data of meadow steppe and alpine meadow in the Qinghai-Tibet Plateau (QTP) for the period 2015–2019. Our results show that AGB for both grasslands increased, but BGB stayed steady over 5 years. The rising tendency of AGB was caused by the upward trend of AGB in forbs and grasses, which are the dominant functional groups in QTP, stressing the importance of dominant functional groups to ecosystem functioning. The biodiversity-ecosystem functioning relationships were significantly positive for AGB, stable for BGB, and negative for the BGB:AGB ratio, which highlights the crucial role of higher species richness in ecosystem functioning. Significant differences in mean species richness among sites (9–19 species in meadow steppe and 8–22 species in alpine meadow) highlight the varying levels of species diversity across sites in the QTP. While 42% of the sites showed stable species richness, the reported increasing trends in species richness at 58% of the sites indicate the potential for ecological changes or processes in these areas. AGB in both grasslands increased, while BGB remained stable with increasing precipitation. The top soil layer (0–10 cm) dominated the observed BGB in both grasslands, as abundant nutrients in the top layer provide favorable conditions for root proliferation. In meadow steppe, AGB formed an isometric relationship with BGB, indicating that AGB increased with BGB. This study concludes that species richness influenced ecosystem functioning, and forbs and grasses dominated biomass productivity, of which the topsoil layer contributed three-quarters of BGB. Our study (i) provides empirical evidence of stable to increasing species richness in both grasslands over 5 years, and (ii) highlights the role of greater species richness in enhancing ecosystem functioning. These findings serve as a scientific reference for policymaking regarding ecosystem stability.

Simultaneously Regulating Electrochemical Corrosion Behavior and Wettability of Magnesium-Neodymium Alloy by Self-Layered Chemical Conversion Coating.

Rapid corrosion in aqueous solutions of magnesium alloys is one of the major obstacles to their wide application, and coating plays a crucial role in their corrosion protection. Recently, protection- and function-integrated coatings have attracted much attention in the research field of magnesium alloys. In this work, a simple chemical conversion process is proposed to fabricate a composite coating on a magnesium-neodymium alloy through immersion in an aqueous solution made of Ca(OH)2 and NaHCO3. After the immersion process, a coating consisting of two spontaneously formed layers is acquired. The top flower-like layer is composed of Mg5(OH)2(CO3)4∙4H2O, Mg(OH)2 and CaCO3, and the inner dense layer is speculated to be Mg(OH)2. Electrochemical impedance spectroscopy, polarization tests, and hydrogen evolution are combined to evaluate the corrosion resistance in simulated body fluid, simulated seawater solution, and simulated concrete pore solution, which reveals that the coated sample has better corrosion resistance than the uncoated one. After the coated sample is modified with fluorinated silane, a water-repellent surface can be achieved with an average water contact angle of 151.74° and a sliding angle of about 4°. Therefore, our results indicate that effective corrosion protection and potential self-cleaning ability have been integrated on the surface of the magnesium alloy in this study. In addition, the formation mechanism of the self-layered coating is discussed from the viewpoint of the interaction between the substrate and its external solution.

Soil organic matter and total nitrogen as key driving factors promoting the assessment of acid-base buffering characteristics in a tea (Camellia sinensis) plantation habitat.

The issue of soil acidification in tea plantations has become a critical concern due to its potential impact on tea quality and plant health. Understanding the factors contributing to soil acidification is essential for implementing effective soil management strategies in tea-growing regions. In this study, a field study was conducted to investigate the effects of tea plantations on soil acidification and the associated acid-base buffering capacity (pHBC). We assessed acidification, pHBC, nutrient concentrations, and cation contents in the top 0-20cm layer of soil across forty tea gardens of varying stand ages (0-5, 5-10, 10-20, and 20-40years old) in Anji County, Zhejiang Province, China. The results revealed evident soil acidification due to tea plantation activities, with the lowest soil pH observed in tea gardens aged 10-20 and 20-40years. Higher levels of soil organic matter (SOM), total nitrogen (TN), Olsen phosphorus (Olsen-P), available iron (Fe), and exchangeable hydrogen (H+) were notably recorded in 10-20 and 20-40years old tea garden soils, suggesting an increased risk of soil acidification with prolonged tea cultivation. Furthermore, prolonged tea cultivation correlated with increased pHBC, which amplified with tea stand ages. The investigation of the relationship between soil pHBC and various parameters highlighted significant influences from soil pH, SOM, cation exchange capacity, TN, available potassium, Olsen-P, exchangeable acids (including H+ and aluminum), available Fe, and available zinc. Consequently, these findings underscore a substantial risk of soil acidification in tea gardens within the monitored region, with SOM and TN content being key driving factors influencing pHBC.

Mapping Topsoil Carbon Storage Dynamics of Croplands Based on Temporal Mosaicking Images of Landsat and Machine Learning Approach

Understanding changes of soil organic carbon (SOC) in top layers of croplands and their driving factors is a vital prerequisite in decision-making for maintaining sustainable agriculture. However, high-precision estimation of SOC of croplands at regional scale is still an issue to be solved. Based on soil samples, synthetic image of bare soil and geographical data, this paper predicted SOC density of croplands using Random Forest model in the Black Soil Region of Jilin Province, China in 2005 and 2020, and analyzed its influencing factors. Results showed that random forest model that integrates bare soil composite images improve the accuracy and robustness of SOC density prediction. From 2005 to 2020, the total SOC storage in croplands decreased from 89.96 to 82.79 Tg C with an annual decrease of 0.48 Tg C yr−1. The mean value of SOC density of croplands decreased from 3.42 to 3.32 kg/m2, and high values are distributed in middle parts. Changes of SOC represented significant heterogeneity spatially. 62.14% of croplands with SOC density greater than 4.0 kg/m2 decreased significantly, and 38.60% of croplands with SOC density between 2.5 and 3.0 kg/m2 significantly increased. Climatic factors made great contributions to SOC density, however, their relative importance (RI) to SOC density decreased from 44.65% to 37.26% during the study period. Synthetic images of bare soil constituted 23.54% and 26.29% of RI in the SOC density prediction, respectively, and the contribution of each band was quite different. The RIs of topographic and vegetation factors were low but increased significantly from 2005 to 2020. This study can aid local land managers and governmental agencies in assessing carbon sequestration potential and carbon credits, thus contributing to the protection and sustainable use of black soils.

Ultrafine Si evaporation control technology to inhibit the island nucleation of epitaxial graphene on SiC (000-1)

The theoretically high mobility of graphene on C-terminated face of silicon carbide (SiC (000-1)) makes it a suitable candidate for electronic devices. However, the quality of graphene grown on SiC (000-1) is always poor. In this paper, we clarify that the partial pressure of silicon is the core parameter to control the nucleation and growth of graphene on SiC (000-1). Therefore, we propose a new system with SiC cap and optimize the height between the SiC cap and the SiC sample to control the partial pressure of silicon. Finally, the high-quality graphene with almost no D peak in Raman spectrum has been obtained. The nanosized domain underlying the top graphene layer has been demonstrated as the source of the defects, which can be inhibited by high partial pressure of silicon. Herein, a special electronic detective mode of electrically biased tapping mode (eb-TM) has been successfully implemented to characterize of the nano-domains underside. Furthermore, in our system, the suitable temperature is from 1350 °C to 1500 °C and the pressure is from 750 Pa to 40 kPa. This broad growth window makes the SiC cap system has greater advantages in the large-scale and stable batch production of epitaxial graphene in the future.

Regulating Cotton Growth via Rhizobium Species

Unpredictable precipitation is a common problem for plant growth in India’s Deccan plateau, which is known for its poor soil and frequent droughts. Critical to the regulation of plant diseases and the enhancement of plant growth are root-colonizing rhizobacteria like Rhizobium. Isolating productive Rhizobium species from soil around the Eturnagram region’s cotton rhizosphere was the goal of a study carried out at Palamuru University. Rhizobium variant-5, currently known as Rhizobium sp. PKS [NCBI-OK663003, NCMR-MCC4960], was one of five different strains of Rhizobium isolated using the top layer method. It showed strong support for the growth of six different cotton cultivars. Out of the six cotton varieties tested, the Mahyco cultivar had the lowest proline levels while having higher amounts of IAA, proteins, chlorophyll, and sugars. The effectiveness of Mahyco was confirmed by experimental field testing conducted in four distinct cotton agricultural soils of Mahabubnagar District using Rhizobium sp. PKS [NCBI-OK663003, NCMR-MCC4960]. Deep black soil showed improved phytohormone synthesis and good biochemical alterations, whereas shallow black soil showed that the strains considerably enhanced plant development. Based on these results, the novel Rhizobium sp. PKS could be used as a bioinoculant in cotton fields on the Deccan plateau, which could improve agricultural yields despite the harsh conditions.

Design and theoretical analysis of SPR biosensors based on gold-silver alloy and protective top layer for enhanced biosensing applications

In this paper, we present a theoretical study to enhance the performance of SPR biosensor structures based on the Kretschmann configuration. We use a low refractive index CaF2 prism, a gold-silver alloy (Au10Ag90), different protective top layers, and water as a sensing medium (SM). Our results show that a structure with CaF2 prism, Au10Ag90, and SM achieves a sensitivity of 280⁰/RIU. The addition of different cover layers to this structure such as graphene, SiO2, BaTiO3, Fe2O3, and Al2O3 improves the sensitivity to 300⁰/RIU, 340⁰/RIU, 340⁰/RIU, 360⁰/RIU, and 420⁰/RIU, respectively. Finally, we conclude that the structure with Al2O3 has the best simulation results in terms of sensitivity of 420⁰/RIU, then Figure of Merit (FoM) of 83.83/RIU, and Quality Factor (QF) of 176.05/RIU. We also discuss the experimental feasibility of this work. The proposed biosensors can be used in different biological sensing applications and specifically, in the detection of cancer bio-markers in body fluids.

The Dependence of Hydrophobic Interactions on the Shape of Solute Surface.

According to our recent studies on hydrophobicity, this work is aimed at understanding the dependence of hydrophobic interactions on the shape of a solute's surface. It has been observed that dissolved solutes primarily affect the structure of interfacial water, which refers to the top layer of water at the interface between the solute and water. As solutes aggregate in a solution, hydrophobic interactions become closely related to the transition of water molecules from the interfacial region to the bulk water. It is inferred that hydrophobic interactions may depend on the shape of the solute surface. To enhance the strength of hydrophobic interactions, the solutes tend to aggregate, thereby minimizing their surface area-to-volume ratio. This also suggests that hydrophobic interactions may exhibit directional characteristics. Moreover, this phenomenon can be supported by calculated potential mean forces (PMFs) using molecular dynamics (MD) simulations, where different surfaces, such as convex, flat, or concave, are associated with a sphere. Furthermore, this concept can be extended to comprehend the molecular packing parameter, commonly utilized in studying the self-assembly behavior of amphiphilic molecules in aqueous solutions.

Development of an electrochemical biosensor with TiN nano-electrode arrays for IL-6 detection

In this study, we developed a novel electrochemical biosensor for detecting IL-6 that uses a nano-electrode array (NEA) fabricated via standard CMOS processing. Miniaturizing the electrodes to the nanoscale and arranging them in an array to form an NEA facilitated the creation of a higher electric field magnitude, compared to that available via the use of microelectrodes, that could be used to improve biosensor sensitivity. Additionally, the array configuration of the NEA aided in providing sufficient reaction sites. Each nano-electrode in the NEA was cylindrically shaped, with a radius of 0.1 µm, and a top layer formed by TiN physical vapor deposition. Each NEA biosensor was divided into four independent banks, with each bank including a set of WE, CE and RE. These banks were capable of independently inputting and outputting electrical signals. This design allowed the NEA biosensor to undergo selective modification by CV input. In this study, we discuss and address material and contamination issues associated with CMOS-produced NEAs and their uses as biosensors. To ameliorate these issues, we stored materials and products in a nitrogen-controlled cabinet and conducted pretreatment cleaning on the electrodes. Both steps had a noticeable impact on the cleanliness of the electrode surfaces. These optimized conditions resulted in a remarkable 96.6 % reduction in Rct. The NEA surface was functionalized by electrochemically grafting diazonium salts subsequently immobilized with anti-IL-6 antibodies via EDC/NHS chemistry. The resulting NEA biosensor demonstrated sufficient sensitivity to rapidly distinguish inflammatory conditions and disease severity. This showcases the potential for using NEA devices mass-produced via standard CMOS processing as electrodes for biosensors.

Changing the order and ratio of substrate filling reduced CH4 and N2O emissions from the aerated constructed wetlands

Constructed wetlands (CWs) have been used to enhance pollutant removal by filling several types of material as substrates. However, research on substrate filling order remains still limited, particularly regarding the effects of greenhouse gas (GHG) emissions. In this study, six CWs were constructed using zeolite and ferric‑carbon micro-electrolysis (Fe-C) fillers to evaluate the effect of changing the filling order and ratio on pollutant removal, GHGs emissions, and associated microbial structure. The results showed that the order of substrate filling significantly impacted pollutant removal performance on CWs. Specifically, CWs filled with zeolite in the top layer exhibited superior NH4+-N removal compared to those filled in the lower layer. Moreover, the highest NH4+-N removal (95.0 % ± 1.9 %) was observed in CWs with a zeolite to Fe-C volume ratio of 8:2 (CWZe-1). Moreover, zeolite-filled at the top had lower GHGs emissions, with the lowest CH4 (0.22 ± 0.10 mg m−2 h−1) and N2O (167.03 ± 61.40 μg m−2 h−1) fluxes in the CWZe-1. In addition, it is worth noting that N2O is the major contributor to integrated global warming potential (GWP) in the six CWs, accounting for 81.7 %–90.8 %. The upper layer of CWs filled with zeolite exhibited higher abundances of nirK, nirS and nosZ genes. The order in which the substrate was filled affected the microbial community structure and the upper layer of CWs filled with zeolite had higher relative abundance of nitrifying genera (Nitrobacter, Nitrosomonas) and denitrifying genera (Zoogloea, Denitratisoma). Additionally, N2O emission was reduced by approximately 41.2 %–64.4 % when the location of the aeration of the CWs was changed from the bottom to the middle. This study showed that both the order of filling the substrate and the aeration position significantly affected the GHGs emissions from CWs, and that CWs had lower GHGs emissions when zeolites were filled in the upper layer and the aeration position was in the middle.

A facile design of porous heat sink optimized thermodynamically for thermo-hydraulic performance

Implementing active cooling through micro-channel heat sinks integrated with printed circuit heat exchangers demands a simultaneous enhancement of thermal and hydraulic performance, all while avoiding complex designs for ease of fabrication. We propose a porous wall embedded double-layered micro-channel heat sink, aiming to decrease the necessary pumping powers while maintaining a minimal impact on the heat transfer rate. Additionally, this design simplifies geometric complexities, enhancing ease of fabrication. We assessed the feasibility of different porous embedded double-layered micro-channel heat sink configurations by evaluating their thermal and hydraulic performance. Our analysis uniquely integrates the principles of the second law of thermodynamics with traditional first law analysis, providing novel insights into heat sink design. We discovered that configuring porous walls solely in the top layer of the double-layered micro-channel heat sink is the only viable option. Furthermore, our analysis reveals that embedding porous walls exclusively in the top layer reduces irreversibility due to frictional losses by 9.13 %, with a slight increase in irreversibility due to heat transfer by 1.55 %, in comparison to the solid double-layered micro-channel heat sink at a flow rate of 1000 ml/min. Moreover, at the same flow rate, compared to configuration with porous walls in both layers, the top layer configuration exhibits improved thermal performance by 17.28 %. Next, we demonstrate that while the first law analysis indicates the viability of the top porous configuration, the second law analysis limits its viability to a certain coolant flow rate range. Finally, we optimize the heat sink design and coolant flow rates, proposing a viable design by simply incorporating porous walls in only the top layer of double layered micro-channel heat sink, which otherwise proved to be non-viable.

What Prevents the Crystallization of Magma from the Roof Downwards in Large Basaltic Magma Chambers?

Abstract A common feature of layered intrusions is the absence of the Upper Border Series (UBS)—a rock sequence that is expected to grow from the roof downwards in large basaltic magma chambers. This is surprising because magma cooling occurs predominantly through the roof of magma chambers. The lack of the UBS is thus indicative of some fundamental reason that prevents basaltic magmas from crystallizing at the chamber roof. Here, we propose that this could be attributed to a layer of anatectic granitic melt that develops on the top of evolving basaltic chambers. The layer may be formed by partial melting of silica-rich crustal rocks in response to the upward transfer of heat from the crystallizing magma. The heat transfer takes place through the initial UBS, resulting in this unit becoming suspended between two buoyant liquids: granitic melt above and basaltic melt below. This unstable position leads to the disruption of the UBS and its collapse onto the temporary chamber floor. A two-layer magma system thus forms, with a light granitic melt floating atop a denser basaltic magma. The granitic melt is expected to be superheated with respect to its liquidus temperature via heat transfer from the underlying basaltic magma. In the absence of a solid surface at the top of the basaltic magma layer, the growth of the UBS cannot resume due to the lack of a solid place for new crystals to attach. Further crystallization of basaltic magma may therefore only continue from the base upwards, producing a layered intrusion that consists of only floor rock sequences.

A mid-infrared ultra-wideband polarization-independent tunable perfect absorber based on Dirac metal materials

A mid-infrared ultra-wideband tunable terahertz absorber based on bulk Dirac semimetal (BDS) is presented. It has a simple three-layer structure: a top BDS metal layer, a middle dielectric layer, and a bottom reflective metal layer. The BDS layer was designed by creating a square cavity and a long rectangular cavity in the center of the BDS rectangle. The long rectangle was then rotated by 90° to form a centrosymmetric cavity. Using CST Studio Suite software, we numerically simulate the absorption characteristics. The simulation results indicate that the absorber achieves a high absorption (>90 %) of about 47.59 THz in the range of 37.5–90 THz when the Fermi energy level is 70 meV. The average absorption exceeds 95 %. In addition, adjusting the Fermi energy level of the BDS alters the absorption bandwidth. The centrosymmetric design of the structure ensures the absorber exhibits insensitivity to different polarization modes and angles of incidence, as well as excellent absorption stability. The designed shock absorber also exhibits excellent tolerance in manufacturing, reducing fabrication challenges and enabling practical applications. In addition, our design possesses the unique ability to modulate light in the mid-infrared band. These remarkable properties position our findings with significant potential in fields such as spectral analysis, optical biosensing technology, infrared sensing, and related applications.

Heterogenous phase evolution and mechanical response in additively manufactured low alloy martensitic steel processed via laser-directed energy deposition

This work investigates complex heterogeneity in microstructure and mechanical properties of a low alloy martensitic steel fabricated via laser-directed energy deposition (L-DED). A multi-scale characterization starting from macro-scale optical micrography, micro-scale X-ray diffraction and electron backscatter diffraction mapping to nano-scale transmission electron microscopy was adopted to fully comprehend the microstructural heterogeneity along the build direction. Notably, the top layers of the build demonstrated enhanced mechanical properties, exhibiting hardness of around 550 HV and an ultimate tensile strength of 2 GPa, which decreased progressively towards the base. Interestingly, resurgence in strength and hardness was observed for the layers located 10 mm above the substrate. The primary solidification cycle led to the formation of untempered martensite having high strength and hardness while subsequent reheat cycles led to the alteration of these martensites, enhancing ductility at the expense of strength. Auto-tempering and carbide (Fe-C based) precipitation due to prolonged thermal exposure contributed to the increased the strength in the lower layers. Additionally, the temperature profiles during the L-DED thermal cycles were modeled and correlated with the observed phase transformations, allowing for a detailed understanding of the structure–property relationships at different heights within the build. This study provides a fundamental insight into the microstructural heterogeneities and their implications on the strengthening mechanisms in L-DED fabricated low-alloy martensitic steel.

A new mobile diagnosis system for estimation of crop disease severity using deep transfer learning

Crop diseases pose as a major threat to global food security. Minimizing disease-induced damage during crop growth and optimizing crop yields are vital for agricultural sustainability. Therefore, advanced disease detection and prevention of such diseases are crucial and the detection must be prompt and efficient as it is essential for the implementation of appropriate control measures. In this work, a parallel deep learning framework based on deep feature fusion is developed to precisely identify the severity of crop diseases. The framework utilizes ResNet50 and Xception as separate branches for feature extraction. Convolutional layer weights are initialized through transfer learning techniques employing models pre-trained on the ImageNet dataset. A fine-tuning strategy is employed for the optimization of convolutional layers and the design of the top layer. This framework achieves an accuracy of 88.58% on the AI Challenger 2018 dataset, marking an enhancement of 2.8% and 13% over other influential deep learning models, and it also outperforms some recent works. Likewise, the framework exhibits a recognition accuracy of 99.53% on the PlantVillage dataset. Moreover, an Android-based application is developed to diagnose the severity of crop diseases in real-time. The diagnostic system swiftly procures results and provides control recommendations through the capture and upload of images to the platform. The advanced severity detection system reduces the expertise required from users, facilitating precise prevention and control measures whilst focusing on accessibility. This work aims to provide innovative approaches and solutions for disease detection in the agricultural field, utilizing artificial intelligence to enhance agricultural informatization and creating more sustainable farming methods.

Tunable mid-infrared broadband absorption in the atmospheric window of wavelength in 3–5 μm using VO2 phase transition in a three-layer metamaterial

Tunable metasurfaces have garnered considerable attention for their remarkable ability to manipulate electromagnetic waves within carefully designed nanostructures. Achieving resonant absorption requires precise control over the geometry and size of micro-nano structures. This study introduces a highly versatile metasurface platform that leverages the unique phase transition properties of vanadium dioxide (VO2) for controlled absorption. Our design features a planar layered structure with a 0.1 μm thick VO2 top layer, enabling tunability in both thermal and intensity aspects. We demonstrate significant tuning of broadband light absorption across the mid-infrared spectrum, with absorption rates ranging from approximately 30 %–98 % in the critical atmospheric infrared window of 3–5 μm. This range is crucial for infrared sensing, imaging, and communication applications. Notably, the absorption rate increases as the temperature decreases, indicating a positive shift in dynamics, for which we provide a physical explanation. Numerical simulations highlight the ability to control absorption bandwidth by adjusting the thickness and temperature of VO2 layer. These adaptable broadband absorbers hold significant promise for a diverse range of applications, including absorption filters, thermal emitters, thermos photovoltaics, and thermal imaging. Furthermore, the introduced thermally switchable, spectrally selective metamaterials can find applications in dynamic infrared camouflage and active radiative thermal management, opening new horizons in the realm of metamaterial-based technologies.

Field-Free Spin-Orbit Torque Magnetization Switching in a Single-Phase Ferromagnetic and Spin Hall Oxide.

Current-induced spin-orbit torque (SOT) offers substantial promise for the development of low-power, nonvolatile magnetic memory. Recently, a single-phase material concurrently exhibiting magnetism and the spin Hall effect has emerged as a scientifically and technologically interesting platform for realizing efficient and compact SOT systems. Here, we demonstrate external-magnetic-field-free switching of perpendicular magnetization in a single-phase ferromagnetic and spin Hall oxide SrRuO3. We delicately altered the local lattices of the top and bottom surface layers of SrRuO3, while retaining a quasi-homogeneous, single-crystalline nature of the SrRuO3 bulk. This leads to unbalanced spin Hall effects between the top and bottom layers, enabling net SOT performance within single-layer ferromagnetic SrRuO3. Notably, our SrRuO3 exhibits the highest SOT efficiency and lowest power consumption among all known single-layer systems under field-free conditions. Our method of artificially manipulating the local atomic structures will pave the way for advances in spin-orbitronics and the exploration of new SOT materials.

Optimal reinsurance under a new design: two layers and multiple reinsurers

We investigate the optimal reinsurance problem considering a more realistic two-layer design involving excess-of-loss reinsurance and multiple reinsurers. Unlike the commonly assumed single-layer design in the existing literature, our approach involves a top layer consisting of excess-of-loss reinsurance and the involvement of multiple reinsurers. Our focus is on the insurer's management of risk exposure and costly capital reinvestment strategies to maximize the company value. We formulate this problem as an optimization problem with constrained multivariate reinsurance exposure variables, and capital injection control. Our findings show that, from a profitability standpoint, when the surplus is low and the excess-of-loss reinsurance is not too expensive, the insurer should obtain a two-layer reinsurance with an excess-of-loss reinsurance at the top layer and a combination of proportional reinsurance from multiple reinsurers at the bottom layer. In contrast, when the surplus is relatively large or the excess-of-loss reinsurance is too expensive, the insurer should purchase a single-layer proportional reinsurance from multiple reinsurers. When the surplus is large enough, the insurer should not acquire any reinsurance. Our results suggest that stand-alone excess-of-loss reinsurance is never optimal when there is also proportional reinsurance with a variance premium principle available for losses below the excess threshold, and we theoretically confirm that a multi-layer reinsurance design is preferable over a single-layer design. Furthermore, our results demonstrate that in order to maximize the company's value, dividends should be paid according to the lump-sum barrier strategy, and capital injections should be considered only if the surplus is null and the transaction costs on capital injections are not too high.