Layering Research Articles

Nonlinear Optical Bistability Based on Surface Plasmons with Nonlinear Dirac Semimetal Substrate

In this paper, we theoretically investigated the low-threshold and controllable optical bistability (OB) of a graphene-based Otto configuration with a nonlinear three-dimensional Dirac semimetal (3D DSM) as the substrate. The combined effect of the excitation of surface plasmon polaritons (SPPs) in graphene and the very high third-order nonlinear conductivity of the 3D DSM enabled this scheme to achieve a relatively low optical bistability threshold. At the same time, this simple multilayer structure showed the tunability of OB due to the fact that the reflectance could be modulated by regulating the Fermi energy of the 3D DSM. Furthermore, we also found that the OB hysteresis curve was closely related to the relaxation time of the 3D DSM and the thickness of the air layer. We believe that this multilayer configuration could provide a reference idea for devising a bistable device.

Plant Growth Regulators and Rooting Media: A Viable Approach for Growth and Performance of Citrus

Plant growth regulators accompanied with appropriate growth medium can boost up the growth and performance of plants to a greater extent. PGRs such as auxin, gibberellin and cytokine play an exaggerative role in growth and development of the citrus. Moreover, the study reflects a clear overview of the impact of PGRs and different growth media to encourage rooting percentage, number of leaves, survival percentage, sprouting time, and root length of citrus cuttings. Citrus is a versatile fruit crop having a huge number of varieties, cultivars, and species; comes in different colours and flavours. Although, there are different methods used in the multiplication of citrus plant which includes budding, grafting, cutting, air layering, etc. However, propagation by cutting technique is the most commercial and farmer’s friendly approach. Different elements such as concentration of PGRs, age of plants and environmental factors are responsible for the successful growth of the citrus cuttings. Naphthalene acetic acid (NAA) and indole-3-butyric acid (IBA) are the two types of auxin, which are most commonly utilized in citrus propagation. Rooting medium plays a crucial role in the supply the minerals and availability of water in citrus. An absolute rooting medium must have more enough nutrients and water holding capacity with better drainage as well as sufficient air spores for excellent gaseous exchange that fruitfully influence the rooting ability and also have a profound effect on growth and development in citrus cutting. The best time for cutting of citrus stems is in between the July and August.

Vegetation–edaphic correlation and importance value index in himalayan ‘ecotone’ temperate conifer forest using the multivariate technique

Himalayan ‘Ecotone’ temperate conifer forest is the cradle of life for human survival and wildlife existence. In spite of the importance of these areas, they have not been studied in depth. This study aimed to quantify the floristic structure, important value index (IVI), topographic and edaphic variables between 2019 and 2020 utilizing circular quadrant method (10 m x 10 m). The upper-storey layer consisted of 17 tree species belongs to 12 families and 9 orders. Middle-storey shrubs comprised of 23 species representing 14 families and 12 orders. A total of 43 species of herbs, grasses, and ferns were identified from the ground-storey layer, representing 25 families and 21 orders. Upper-storey vegetation structure was dominated by Pinus roxburghii (22.45 %) and middle-storey by Dodonaea viscosa (7.69 %). However, the ground layer vegetation was diverse in species composition (43 species) and distribution. The floral vegetation structure was encompassing of three floral communities which were diverse in IVI, such as, in Piro–Aial (Group 2), Pinus roxburghii (54.46 x 15.94) had the highest IVI value, followed by Pinus wallichiana (45.21 x 14.85) in Piwa–Quin (Group 3) and Ailanthus altissima (22.84 x 19.25) in Aial–Qugal (Group 1). However, the IVI values for Aesculus indica, Celtis australis, and Quercus incana in Aial–Qugal (Group 1) were not determined due to low detection rate. Nevertheless, eleven of these species showed 0 IVI values in Piro–Aial (Group 2) and Piwa–Quin (Group 3). CCA ordination biplot illustrated the significant differences among floral communities and its distribution, which impacted by temperature, rainfall, soil pH, altitude, and topographic features. Ward's agglomerative clustering finding reflected 'Ecotone' temperate conifer forest is rich and diverse floristic structure.

Atmospheric ground layer pollution by suspended solid particles in areas with different technogenic loads

Introduction. According to the World Health Organization ambient air pollution causes enormous harm to public health around the world. Atmospheric solid suspended particles are a heterogeneous mixture of substances with various dimensional, qualitative and quantitative parameters. They are a key indicator of air pollution, contributing to the bronchopulmonary pathology formation. At the moment, there is no general recommended ranking of the solid suspended particles amount in the atmospheric air.Aim. Determination of the SSP fractional content in the air ground layer in high and relatively low technogenic load areas of Vladivostok.Materials and methods. Atmospheric air samples were taken «in the breathing zone» using an electric aspirator. In the granulometric analysis of SSP, the particle size distribution, expressed as a percentage, and the mass concentration of fractions (μg/m3 ) were determined. The ranges of dimensions have been identified, taking into account the solid suspended particles possible origin and the expected pathophysiological features of their effect on the organism.Results. An area with a high technogenic load is characterized by the prevalence of particles with a diameter of up to 10 microns, which have the most pathogenic effect on the organism. In an area with a relatively low technogenic load, particles of larger fractions (10-25, 1000-2000 microns) predominate.Conclusion. Studying the solid suspended particles parameters in specific areas and establishing their influence cellular mechanisms can help in the development of new strategies for the prevention of environmentally-related pathologies.

Design and evaluation of thermal insulation of air layer for sentry building envelopes

The prevalence of small-scale structures, such as sentry buildings, has become widespread, with many of these buildings exposed to the outdoor environment and exhibiting suboptimal thermal insulation in their envelopes. Through a comprehensive study of outdoor disturbances, the most unfavourable envelope was identified. In light of this finding, we have designed static air layer sentry buildings (SAL-SB) and dynamic air layer sentry buildings (DAL-SB). The study conducted experiments and numerical simulations to evaluate the impact of air layer thickness, vent opening forms, and inlet velocities on the thermal insulation of sentry buildings. The results showed that both the SAL and DAL effectively improved thermal insulation, and a thickness of 25 cm has been found to offer the best thermal insulation. However, considering the balance between thermal insulation and cost-effectiveness, a thickness of 15 cm is recommended. Additionally, for DAL, an inlet velocity of 3 m/s is the threshold for switching the heat transfer direction on the roof. These findings provide novel insights into enhancing the thermal environment.

Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips.

Superhydrophobic surfaces (SHS) offer versatile applications by trapping an air layer within microstructures, while water jet impact can destabilize this air layer and deactivate the functions of the SHS. The current work presents for the first time that introducing parallel hydrophilic strips to SHS (SHS-s) can simultaneously improve both water impalement resistance and drag reduction (DR). Compared with SHS, SHS-s demonstrates a 125% increase in the enduring time against the impact of water jet with velocity of 11.9 m/s and a 97% improvement in DR at a Reynolds number of 1.4 × 104. The key mechanism lies in the enhanced stability of the air layer due to air confinement by the adjacent three-phase contact lines. These lines not only impede air drainage through the surface microstructures during water jet impact, entrapping the air layer to resist water impalement, but also prevent air floating up due to buoyancy in Taylor-Couette flow, ensuring an even spread of the air layer all over the rotor, boosting DR. Moreover, failure modes of SHS under water jet impact are revealed to be related to air layer decay and surface structure destruction. This mass-producible structured surface holds the potential for widespread use in DR for hulls, autonomous underwater vehicles, and submarines.

Numerical Simulation on Dispersion of Hydrogen Leaked in Particle Layers of Glass Beads and Soil

In order to understand the dispersion of hydrogen (H2) leaked in packed beds of nonporous/porous particles in a partially open space practically, the dispersion of H2 in the particle layers of glass beads and soil was analytically studied using a computational fluid dynamics code to be compared with the experiments and to elucidate the effects of the particle layer. The packed beds in the partially open space can be considered as a basic model for all processes of transfer, treatment, storage, and disposal of radioactive materials containing fuel debris in the decommissioning of nuclear facilities after a severe accident. The H2 flowing out from a single leak point in the particle layer of nonporous glass beads was affected by buoyancy around the leak point and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, the H2 spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H2 concentration became about 1/3 or less of the concentration near the surface of the particle layer. When the particle diameters were 512 μm and 1200 μm, this tendency was more pronounced when the porosity was the same and the particle diameter was smaller. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H2 in the particle layer proceeded in the same manner as in the case of the glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H2 diffused in the air layer until the H2 concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of the H2 concentration distribution. Based on this information, we further simulated H2 behavior in the vessel containing the H2 leaked particle layer. By inserting multiple vent pipes without considering H2 generation distribution and particle properties in the particle layer, H2 accumulated from one pipe was discharged by buoyancy without depending on the H2 generation distribution and particle properties in the particle layer and air flowed in from the other pipe. It was suggested that such a natural ventilation process would reduce the H2 concentration in the container.

CONSERVATION OF A PAINTED WOODEN COFFIN AT DAHSHUR ARCHAEOLOGICAL AREA

This paper aims to document the conservation processes of a polychrome wooden coffin in the Dahshur archaeological area dating back to the late period. The exterior part of the coffin is decorated with a painted layer. Visual observation, 2D Program, and Optical Microscopy (OM) were used. wood identification. The coffin was in a bad condition. It was covered with a thick layer of dust, losing parts of the painted and gesso layers, as well as other parts of these layers, were lost. Some parts were missing from the head area of the lid coffin. The conservation processes of the wooden coffin included mechanical and chemical cleaning, reattachment of the separated parts of the ground layer and painted layers, filling the edge of the painted layer, and consolidating the painted layer. The conservation process included mechanical cleaning using soft brushes, chemical cleaning using ethyl alcohol and distilled water for painting, stabilization of the separated gesso layer using Paraloid B72, filling cracks of the gesso layers using glass microballoon with Paraloid B72 and consolidating the painted layer with calcium oxide nanoparticles with Klucel G (hydroxypropyl cellulose) 0. 5%

Performance evaluation of ground layer adaptive optics based on layer correction efficiency.

Ground layer adaptive optics (GLAO) has been widely employed in wide-field observations with ground-based telescopes. However, the present evaluation of GLAO performance lacks a criterion in terms of turbulence layer correction. This deficiency results in a significant gap in understanding the effectiveness of GLAO correction at different heights of the turbulence layer, thereby hindering the optimization of GLAO system performance. To bridge this gap, this Letter introduces a new, to the best of our knowledge, performance criterion for GLAO, termed layer correction efficiency (LCE). This criterion is formulated to quantify the effective compensation of the GLAO system for a specific altitude layer of turbulence, providing support for the further enhancement of GLAO performance. The simulation results indicate that the LCE has high applicability in GLAO performance analysis.

Broadband directional filter in multilayer liquid crystal polymer films at W-band

In this work, a four-port directional filter (DF) with a broad passband and low reflection is proposed at the W-band, which comprises three unit filters at 92, 95, and 97 GHz, cascaded in series. Each unit consists of two microstrip lines in the top circuit layer for signal input and output, two pairs of apertures in the middle ground layer for directional coupling, and one square loop in the bottom layer as a selective resonator. By sweeping the working frequencies of the three units and optimizing the phase delays between them, the proposed filter achieves a 3-dB bandwidth as broad as 16%, an insertion loss of 2.5 dB at 95 GHz, and an out-of-band rejection of −28 and −23 dB at 80 and 110 GHz, respectively. The corresponding reflection attenuation is larger than 9.6 dB from 60 to 105 GHz. To verify our design, a prototype is fabricated and characterized, and its experimental data are consistent with the simulation. This work significantly expands the bandwidth of DFs and may find many applications in frequency division multiplexing and high-gain wireless systems.

Research and Development of Inland Green and Smart Ship Technologies in China

Nowadays, the development of green and smart ships has become a trend in the global shipping industry. Some countries such as Japan and Korea, as well as several European countries, have already made some progress and advantages. In recent years, China has issued a series of policies to encourage and support the development of green and smart ships. Beyond that, the demonstration of green and smart ships has been promoted along with the trend of larger-sized and standardized inland vessels. The Chinese status and plans of green technologies are summarized including air layer drag reduction, efficient propulsion, DC networking, and clean energy. Some smart technologies have also been illustrated, for instance, intelligent driving, intelligent engine rooms, energy efficiency, hulls, cargo control, and information integration. Smart ship technologies need to be fully validated in order to improve industrialization applications. In the shipping industry, the development and application of smart ship technology need international and inter-regional cooperation, so as to achieve much higher energy savings, ensure environmental protection, achieve collaborative intelligence, and ensure safety and reliability. In turn, this will aid economic advances worldwide.

Study on Carbonation of Porcine Blood Hydrogel in the Composite Mortar of Ancient Chinese Architectural Painting.

In the ancient Chinese recipe for composite mortar used in the construction of ground layers for architectural painting, the mixture of porcine blood and lime water is one of the constituent materials. Herein, according to the traditional recipe, the interaction between porcine blood and lime water was systematically and deeply investigated. The experimental investigation demonstrated that porcine blood mixed with lime water at the ratio found in the recipe can form a hydrogel with a hydrophobic surface. During air-drying, the lime water in porcine blood hydrogel can react with CO2 to form calcium carbonate. The crystal morphology of the formed calcium carbonate depends on the surrounding micro-environment of calcium ions in the porcine blood hydrogel. The formed morphology of calcium carbonate includes small calcite crystallites, small graininess calcite crystals with round features, calcite aggregates with layered ladder-like structures, and amorphous calcium carbonate (ACC). Interestingly, the calcium carbonate formed in the inner part of the porcine blood hydrogel exhibits lamellar distribution due to a Liesegang pattern formation. Based on the findings that the porcine blood hydrogel has surface hydrophobicity and brittleness, it can be predicted that in the preparation process of composite mortar for ancient building color painting base course, porcine blood used in the form of a hydrogel is not only easier to be dispersed in hydrophobic tung oil than in liquid porcine blood but also the affinity between porcine blood gel and tung oil is enhanced. As constituent material dispersed in the composite mortar, the layered distribution of calcium carbonate in the porcine blood hydrogel may presumably be beneficial to reduce the internal stress of the composite mortar material.

A five-band terahertz metamaterial absorber with properties of polarization-insensitive and wide-angle tolerance based on bulk Dirac semimetal

We design a bulk Dirac semimetal (BDS) metamaterial-based terahertz absorber consisted of a BDS layer, a dielectric layer and a gold grounding layer from top to bottom, which produces five excellent terahertz absorption peaks having 99.55%, 99.63%, 99.65%, 97.72%, and 99.87% absorption at 0.49 THz, 0.85 THz, 1.68 THz, 2.00 THz, and 2.27 THz, respectively. The five-band BDS-based absorber is polarization-insensitive and wide-angle tolerance, with good absorption in the incident angle range of 0°–60°. The tuning of the Fermi energy level of BDS in the range of 40–70 meV enables the dynamic adjustment of absorption frequencies and absorption rates of these peaks. We also analyze the refractive index sensing sensitivity of five-band BDS-based absorber, it is revealed that when the refractive index of surrounding analyte is changed from 1.0 to 1.8, the refractive indices of the five absorption peaks are 57.75 GHz/RIU, 107.25 GHz/RIU, 101.75 GHz/RIU, 101.75 GHz/RIU, and 134.75 GHz/RIU, which approximately exhibit an enhanced sensing sensitivity as the absorption frequency increases. The design is simultaneously characterized by multiple bands, high absorption, high stability,and high refractive index sensitivity, which should have great potential for application in the fields of terahertz technology.

On the use of dispersion curves to determine the critical speed of railway tracks. Application to case studies

Trains may reach a so-called critical speed at which, in the absence of damping, the dynamic response of the entire railway infrastructure would grow without any bound. A train will have less impact on the track the more its speed is lower than the critical speed. Therefore, in terms of track maintenance, it is of vital importance to know the critical speed along the track before its construction.Following the results mathematically proved by Kausel et al. (2020), we present a procedure —referred to as the “CSC method”— to determine the critical speed of railway tracks. It is based on the dispersive characteristics of the railway track system, which consists of the track bed layers (including the ballast, subballast and form layers among others), the embankment and the foundation ground (which can be arbitrarily layered). We validate the CSC method by using measurements from the well-known real case of Ledsgard (Sweeden). This method is easier to be implemented than dynamic FEM models and requires less geotechnical parameters and computational time.The CSC method is applied to some case studies: We use it to estimate the critical speed of a typical high-speed line and to study the influence on the critical speed of (i) the height of the embankment and (ii) the presence and thickness of an upper ground layer with low shear wave velocity. In addition, the critical speed inferred for the typical high-speed line is corroborated with experimental results from a railway testing facility at 1:1 scale, which can be interpreted as further validation of the CSC method. Moreover, the robustness of this method is demonstrated by the fact that the trend of results from the latter calculations (cases i and ii) agrees with the expected ones.

Fire facilitates ground layer plant diversity in a Miombo ecosystem.

Little is known about the response of ground layer plant communities to fire in Miombo ecosystems, which is a global blind spot of ecological understanding. We aimed: (1) to assess the impact of three experimentally imposed fire treatments on ground layer species composition and compare it with patterns observed for trees; and (2) to analyse the effect of fire treatments on species richness to assess how responses differ among plant functional groups. At a 60-year-long fire experiment in Zambia, we quantified the richness and diversity of ground layer plants in terms of taxa and functional groups across three experimental fire treatments of late dry-season fire, early dry-season fire and fire exclusion. Data were collected in five repeat surveys from the onset of the wet season to the early dry season. Of the 140 ground layer species recorded across the three treatments, fire-maintained treatments contributed most of the richness and diversity, with the least number of unique species found in the no-fire treatment. The early-fire treatment was more similar in composition to the no-fire treatment than to the late-fire treatment. C4 grass and geoxyle richness were highest in the late-fire treatment, and there were no shared sedge species between the late-fire and other treatments. At a plot level, the average richness in the late-fire treatment was twice that of the fire exclusion treatment. Heterogeneity in fire seasonality and intensity supports diversity of a unique flora by providing a diversity of local environments. African ecosystems face rapid expansion of land- and fire-management schemes for carbon offsetting and sequestration. We demonstrate that analyses of the impacts of such schemes predicated on the tree flora alone are highly likely to underestimate impacts on biodiversity. A research priority must be a new understanding of the Miombo ground layer flora integrated into policy and land management.

Analytical solutions for single and multiple scattering from rib-stiffened plates in water.

The interaction of an acoustic plane wave with a pair of plates connected by periodically spaced stiffeners in water is considered. The rib-stiffened structure is called a "flex-layer" because its low frequency response is dominated by bending stiffness. The quasi-static behavior is equivalent to a homogeneous layer of compressible fluid, which we identify as air for the purposes of comparison. In this way, an air layer is acoustically the same as a pair of thin elastic plates connected by a periodic spacing of ribs. At discrete higher frequencies, the flex-layer exhibits perfect acoustic transmission, the cause of which is identified as fluid-loaded plate waves propagating back and forth between the ribs. Both the low and finite frequency behavior of the flex-layer are fully explained by closed-form solutions for reflection and transmission. The analytical model is extended to two flex-layers in series, introducing new low and high frequency phenomena that are explained in terms of simple lumped parameter models.

Study on the source of overtone series in a harmonica note

The harmonica reed is a cantilever beam and therefore does not produce integer harmonics. High-speed camera video of the reed and vibrometer measurements both demonstrate this expected behavior at the reed tip when being played. However, the acoustical recording shows an integer overtone series with large amplitudes (<10 dB from the fundamental) all the way past 22 kHz. To understand this phenomenon, we eliminated resonant cavities and other possible acoustic feedback systems by plucking the reed with only the reed plate attached. The acoustical and vibrometer data showed the same discrepancy in this case, but only when the reed enters the reed slot in the reed plate. The overtones don’t show up when the reed is vibrating completely away from the reed slot. In this paper, we will present these data and show how this phenomenon could be a result of vorticity produced by the sharp edge of the plate and the small air layer gap between plate and reed.

Extended scene deep-phase-retrieval Shack-Hartmann wavefront sensors

Context. Strong atmospheric turbulence has been a challenge for high-resolution imaging of solar telescopes. Adaptive optics (AO) systems are capable of improving the quality of imaging by correcting partial aberrations. Thus, the performance of Shack-Hartmann sensors in measuring aberrations generally determines the upper performance bound of AO systems. In solar AO, classic correlation Shack-Hartmann sensors only correct a small number of modal aberrations. Moreover, strong aberrations are difficult to measure stably by correlation Shack-Hartmann. In this context, the improvement in the performance of Shark-Hartmann sensors promises to enable higher-resolution imaging of extended objects for ground-based telescopes or Earth observation. Aims. We propose a new extended scene deep-phase-retrieval Shack-Hartmann wavefront sensing approach to improve the image quality of solar telescopes. It is capable of achieving high-accuracy measurements of high-spatial-resolution wavefronts on extended scene wavefront sensing. Moreover, it has great generalization when observing unknown objects from different fields of view of the telescope. Methods. Our proposed approach can extract features resembling the sub-aperture point spread function (PSF) from a Shack-Hartmann sensor image without any prior information. Then a convolutional neural network is used to establish a nonlinear mapping between the feature image and the wavefront modal coefficients. The extracted feature greatly eliminates the shape information of the extended object while maintaining more information related to aberrations. We verified the performance of the proposed method through simulations and experiments. Results. In the indoor experiment on the ground layer adaptive optics (GLAO) of the 1 m New Vacuum Solar Telescope, compared to the Shack-Hartmann correlation method, the proposed method reduces the correction errors by more than one third. When observing objects from different fields of view in the GLAO that differ from the object in the training data, the relative errors fluctuate within the range of 20% to 26%. The AO system with the proposed wavefront measurement method can obtain higher-resolution focal images of the simulated solar granulation after a round of offline correction. The average latency of the proposed method is about 0.6 ms.

Five-Band Tunable Terahertz Metamaterial Absorber Using Two Sets of Different-Sized Graphene-Based Copper-Coin-like Resonators

In this paper, a five-band metamaterial absorber with a tunable function in a terahertz band is proposed, which consists of a gold grounding layer, a polyimide dielectric layer, and a periodic patterned graphene layer. The patterned graphene layer is constructed from two sets of copper-coin-shaped structures of different sizes. The designed absorber achieves absorptions of 96.4%, 99.4%, 99.8%, 98.4%, and 99.9% at 4.62 THz, 7.29 THz, 7.70 THz, 8.19 THz, and 8.93 THz, respectively, with an average absorption intensity of 98.78%. The physical mechanism of this five-band absorber was explained by the impedance matching principle and electric field distribution. The absorption performance of the five-band absorber can be effectively tuned by changing the geometry of the patterned graphene array and the thickness of the dielectric layer. Given that the resonant frequency of the absorber varies in proportion to the Fermi level, by varying the Fermi level of the graphene hypersurface, we can achieve the continuous tuning of the absorption performance over a wide frequency range. The five-band absorber has a stable absorption performance over a wide incidence angle of 0–65°, and by combining the merits of high absorption, dynamic adjustability, and a large number of absorption peaks, the given absorber could have great potential for applications in nondestructive testing, imaging, communication, sensing, and detectors.

Study on the Performance of a Surface with Coupled Wettability Difference and Convex-Stripe Array for Improved Air Layer Stability.

The existence of an air layer reduces friction drag on superhydrophobic surfaces. Therefore, improving the air layer stability of superhydrophobic surfaces holds immense significance in reducing both energy consumption and environmental pollution caused by friction drag. Based on the properties of mathematical discretization and the contact angle hysteresis generated by the wettability difference, a surface coupled with a wettability difference treatment and a convex-stripe array is developed by laser engraving and fluorine modification, and its performance in improving the air layer stability is experimentally studied in a von Kármán swirling flow field. The results show that the destabilization of the air layer is mainly caused by the Kelvin-Helmholtz instability, which is triggered by the density difference between gas and liquid, as well as the tangential velocity difference between gas and liquid. When the air layer is relatively thin, tangential wave destabilization occurs, whereas for larger thicknesses, the destabilization mode is coupled wave destabilization. The maximum Reynolds number that keeps the air layer fully covering the surface of the rotating disk (with drag reduction performance) during the disk rotation process is defined as the critical Reynolds number (Rec), which is 1.62 × 105 for the uniform superhydrophobic surface and 3.24 × 105 for the superhydrophobic surface with a convex stripe on the outermost ring (SCSSP). Individual treatments of wettability difference and a convex-stripe array on the SCSSP further improve the air layer stability, but Rec remains at 3.24 × 105. Finally, the coupling of the wettability difference treatment with a convex-stripe array significantly improves the air layer stability, resulting in an increase of Rec to 4.05 × 105, and the drag reduction rate stably maintained around 30%.