Surface Layer Research Articles

Comprehensive Comparison of Seven Widely-Used Planetary Boundary Layer Parameterizations in Typhoon Mangkhut Intensification Simulation

Numerical experiments using the WRF model were conducted to analyze the sensitivity of Typhoon Mangkhut intensification simulations to seven widely used planetary boundary layer (PBL) parameterization schemes, including YSU, MYJ, QNSE, MYNN2, MYNN3, ACM2, and BouLac. The results showed that all simulations generally reproduced the tropical cyclone (TC) track and intensity, with YSU, QNSE, and BouLac schemes better capturing intensification processes and closely matching observed TC intensity. In terms of surface layer parameterization, the QNSE scheme produced the highest Ck/Cd ratio, resulting in stronger TC intensity based on Emanuel’s potential intensity theory. In terms of PBL parameterization, the YSU and BouLac schemes, with the same revised MM5 surface layer scheme, simulated weaker turbulent diffusivity Km and shallower mixing height, leading to stronger TC intensity. During the intensification period, the BouLac, YSU, and QNSE PBL schemes exhibited stronger tangential wind, radial inflow within the boundary layer, and updraft around the eye wall, consistent with TC intensity results. Both PBL and surface layer parameterization significantly influenced simulated TC intensity. The QNSE scheme, with the largest Ck/Cd ratio, and the YSU and BouLac schemes, with weaker turbulent diffusivity, generated stronger radial inflow, updraft, and warm core structures, contributing to higher storm intensity.

Oceanographic preconditions for planning seawater heat pumps in the Baltic Sea – an example from the Tallinn Bay, Gulf of Finland

Abstract. The use of low-temperature seawater heat for renewable energy installations is demonstrated with an example from the Tallinn Bay, Baltic Sea, based on Copernicus Marine Service reanalysis data. Tallinn and its surrounding seaside counties are home to about half a million people and produce about half of Estonia's gross domestic product (GDP). The Tallinn Bay with an area of 223 km2 extends to the north and has an open connection to the Gulf of Finland. Depths more than 50 m that cover the halocline already appear at a distance of 3–4 km from the coast. Surface layers get too cold during winter to be used in heat pumps for district heating; therefore, a feasible option is to pump slightly warmer seawater from the deeper halocline layers. The lowest monthly mean halocline temperature – down to 2.6 °C at 50 m depth and 3.3 °C at 70 m – is found in March and April based on reanalysis data from 1993–2019. The seawater seasonally cools below 3 °C on average on 1 January at 20 m depth and on 12 February at 50 m depth. At the 70 m depth, the average start of T<3 °C was calculated on 28 February, although only 14 winters out of 26 had such water present; in 12 winters the condition T>3 °C was always fulfilled. The median number of cold days is 11, with a maximum of 128 d in the winter 1993/1994 when stratification became rather weak due to the prolonged absence of Major Baltic Inflows of saltier and warmer North Sea waters. During the recent warmer period of 2009–2019, the start of the cold seawater period was delayed on average by 5–10 d. Tallinn has, among other Baltic Sea cities and industrial sites, a favorable location for seawater heat extraction because of the short distance to the unfreezing sub-halocline layers. Still, episodically there are colder-water events with T<3 °C, when seawater heat extraction has to be complemented by other sources of heating energy.

Dynamic Response Analysis of Asphalt Pavement under Pavement-Unevenness Excitation

This paper investigates and analyzes the dynamic response of asphalt pavement under pavement-unevenness excitation based on an orthogonal vector function system and efficient DVP (dual variable and position) method. Firstly, starting from the pavement unevenness of the vehicle excitation source, the pavement-unevenness excitation is established by using the filtered white-noise method, and the random load of the vehicle model is obtained by simulation. Then, based on the basic governing equation of the road-surface problem under the random load, the analytical solution of the road-surface mechanical response is obtained by using the orthogonal vector function system and DVP method. The effects of pavement-unevenness grade, vehicle speed, vehicle load, interlayer contact condition, and transverse isotropy on the mechanical response of the road surface are analyzed via the analytical results. The results show that DVP can effectively solve the dynamic response of pavements under the excitation of pavement unevenness; in addition, it can also be applied to certain situations, such as transverse isotropy of materials and interface conditions. The results show that the pavement unevenness does not affect the average stress and strain of each layer but has a significant effect on the peak value and dispersion degree. An increase in vehicle speed causes a peak in strain and a larger coefficient of variation. Poor bonding between interfaces can lead to increased stress and strain at the bottom of the surface layer.

ДРЕЙФУЮЩИЕ НИТЧАТЫЕ ВОДОРОСЛИ В ПРИБРЕЖНОЙ ЗОНЕ ВОСТОЧНОГО КАСПИЯ КАК САМОСТОЯТЕЛЬНОЕ ВЕРХНЕПЕЛАГИЧЕСКОЕ СООБЩЕСТВО

The coastal zone of the Middle Caspian is currently undergoing significant changes due to falling sea levels. With shallowing, the nature of the influence of water flows on bottom landscapes changes, including the intensification of the impact of storm waves on their surfaces inhabited by bottom communities. The impact of rolling and storm waves on bottom algae is also increasing. Cenoses of bottom macrophyte algae, which was previously growing on underwater rocks, including flat rock platforms, which abound along the eastern coast of the Middle Caspian, at depths of 10-12 m, were previously affected only by particularly strong storm waves. Now their habitats are at a significantly shallower depth (about 7.5-9.5 m), which led to more frequent and massive detachments of macrophyte thalli and their transfer to the pelagic zone. Mass transfer of living thalli of green and red algae to the upper layers of the water column during different seasons of the year led to the formation of communities of a new type, differently structuring the surface layer of the phytopelagic zone. New cenoses are a set of metamorphosed thalli of filamentous algae with a microepiphytic complex abundantly growing on them, live in the surface layer of water for a long time, serve as food for pelagic fish and have a significant impact on coastal landscapes. Mass development of macrophytes on the bottom, and their further intensive development in the pelagic zone, in turn, can be caused by increased eutrophication of the coastal zone in areas of large settlements.

INNOVATIVE APPROACH TO ENSURING THE QUALITY OF GAS TURBINE ENGINE PARTS PRODUCED BY SELECTIVE LASER SINTERING FOR UAV

The research objects are gas turbine engines parts, manufactured using an innovative method of additive manufacturing – selective laser sintering. The main problem solved in this work is the low quality of the surface layer and the residual porosity of the parts obtained by this method, which significantly limits their operational characteristics and durability. As a result of the experimental studies, rational operating parameters of diamond smoothing were established. This allowed to significantly improve the surface quality and increase the operational characteristics of parts made of heat-resistant alloys INCONEL 718 and an intermetallic alloy based on titanium aluminide OX45-3ODS. The effectiveness of diamond smoothing is explained by local plastic deformation and compaction of the surface layer of parts under the influence of high contact pressures and temperatures. This leads to a significant reduction in surface roughness, an increase in the surface hardness due to strain hardening and a significant reduction in the size and number of residual pores. A characteristic feature of the obtained results is the ability to control the quality parameters of the surface layer by varying the diamond smoothing operating parameters – smoothing force, feed, radius, and geometry of the smoother's working part. The established regularities of the smoothing operating parameters have an impact on the quality characteristics of the surface. This information can be utilized in the development of highly efficient technological processes for the production and restoration of gas turbine engines, critical components of unmanned aerial vehicles, obtained through selective laser sintering. Implementing the elaborated technological recommendations will permit broadening the range of goods produced by additive manufacturing and enhancing their capacity and dependability during operation under conditions of cyclical loads and extreme temperatures.

Corrosion Inhibition Potential of Aqueous Extract of Bauhinia acuminata Linn Leaves on Carbon Steel in Hydrochloric Acid Medium

The corrosion of carbon steel in 1 N HCl was analyzed using an aqueous Bauhinia acuminata Linn (BaL) leaf extract. Weight loss method was used to determine the inhibitor efficaciousness and corrosion rate. When dissolved in water, a linneus plant leaf extract exhibit an inhibitory effect which is proportionate to the amount of inhibitors present. It is possible to speed up the corrosion process by increasing the inhibitors’ concentration. Studies have shown that the BaL leaves extract has a 97.30% inhibitory efficiency. By increasing the concentration of inhibitor solutions, a surface layer forms on carbon steel, which inhibits the activity of the active site. The potentiodynamic polarization (PDP) and AC impedance studies (EIS) were employed to examine the mechanical properties of corrosion inhibition. The surface homogeneity and irregularity of carbon steel were examined using AFM and SEM under polished, corroded and inhibitor-treated surfaces. The surface irregularity of the carbon steel were analyzed using atomic force microscopy.

Investigation of Coastal Winds and Turbulence Characteristics Using Doppler Lidar

AbstractSea ports play a major role in the transport of goods worldwide, and knowledge of wind characteristics in these areas is vital to maintaining safety. However, coastal wind flow can be highly complex and turbulent, necessitating additional analysis. A Doppler lidar providing continuous wind profiles is deployed in the Port of Genoa, Italy, to characterize the mean wind velocity and turbulence properties within the coastal surface layer (40–250 m above ground level). Weather conditions, reanalysis data, and transient wind profiles are combined to analyze wind field characteristics on a day which experienced a thunderstorm. We also utilize a method to identify and categorize sources of turbulence through analysis of lidar derived quantities such as wind shear, turbulent kinetic energy, and vertical skewness. Seasonal variations in the wind properties are investigated by selecting data from June (summer) and December (winter). Differences are found in dominant wind direction and the associated frequency of convective mixing, with onshore winds most common in summer and offshore winds in winter. The measured lidar velocity is also compared against Monin–Obukhov similarity theory predictions, showing satisfactory agreement at low heights but struggling to reproduce observations of the stable atmospheric conditions present during winter.

Thermal regime of peatlands in Western Siberia near the southern border of the permafrost

Relevance. The permafrost degradation under the effect of global warming. It determines the necessity for a predictive assessment of permafrost stability to minimize disturbances to engineering installations in the permafrost zone. Aim. To assess the stability of frozen peatlands in the southern part of the zone of insular distribution of permafrost. Objects. Soils of flat-mound and high-mound palsa mires, which preserve permafrost on the southern border of the insular permafrost zone. Methods. Measurements of the temperature of peat and mineral soil in geocryological boreholes from 0 to 10 m deep using the SAM-N automatic monitoring surveillance network; determination of surface temperature from thermal channels of MODIS satellite images from 2000 to 2022; analysis of meteorological indices and determination of air temperature trends for predictive assessment of permafrost stability; calculation of indicator values of permafrost state, such as freezing degree-days and thawing degree-days, frost index, freezing and thawing N-factors. Results. Numerous features of unstable permafrost have been observed. In particular, the mean annual temperature of the surface layer was positive in all studied boreholes (+0.8...+1.3°C), and the temperature at the depth of zero amplitudes (10 m) is close to the melting point (with the predominance of temperatures in the range of –0.2...–0.3°C). Besides, a layer of soil that does not freeze throughout the year (non-merging permafrost) was identified. The thawing degree-days and frost number values correspond to areas with unfrozen soils. Positive trends in air temperature, Earth's surface temperature, and snow depth were observed. For 2000–2022, surface air temperature increased by 0.76°C/10 years on average. The land surface temperature increased in summer by an average of 0.42°C/10 years. If the positive trend in surface air temperatures continues, frozen peatlands in the southern part of the permafrost zone will completely melt in 50–70 years.

MODELING THE PLASTIC DEFORMATION STATE OF THE CONTACT SURFACE DURING FRICTION

The mechanics of contact destruction of compounds during friction under conditions of complex thermodynamic loading was researched. The possibility of a mathematical description of complex damage to friction units and wear intensity is shown, taking into account the peculiarities of the surface layer formation during contact. A method for calculating the surface strength and durability of tribo-compounds is presented. This allows us to relate the parameters of the stressed state of a point (friction coefficient, shape factor) with the thermomechanical parameters of the process. By assessing changes in the friction coefficient and shape parameters, it becomes possible to determine the yield stress and establish structural transformations corresponding to a given stress state.

Characterization of marine heat waves in the Iberia–Biscay–Ireland (IBI) region in 2022

Abstract. Marine heat waves (MHWs) are defined as prolonged periods of anomalously high sea surface temperatures. These events have a profound impact on marine ecosystems, resulting in ecological and economic impacts such as coral bleaching, reduced surface chlorophyll due to increased surface layer stratification, mass mortality of marine invertebrates due to heat stress, rapid species migrations, and fishery closures or quota changes, among others. This research focuses on the study of the MHWs that occurred in the IBI (Iberia–Biscay–Ireland) region during the year 2022, assessing their climatologic properties, analyzing the mean values for the year 2022, and discretizing the events in four subregions representative of the entire domain. Satellite-derived sea surface temperature data were used to detect and characterize the events, revealing that in some areas the year 2022 showed peak anomaly values of (i) 15 MHW events, (ii) 128 d of mean durations, and (iii) 261 total days of MHWs. Through observational and modeling data, the discrete events located in the Bay of Biscay were also examined in the subsurface layers, demonstrating a strong seasonal modulation and heat diffusion through deeper layers, where cold-season events reach higher MHW mean depth values and subsurface positive anomalies of temperature can remain for weeks once an MHW has ended.

Design of a partially narrowed flow channel with a sub-distribution zone for the water management of large-size proton exchange membrane fuel cells

With increased power density and flow field size of proton exchange membrane fuel cells (PEMFCs), water management becomes increasingly important for the exacerbated water accumulation in flow channels (FCs). Therefore, this study proposes a novel partially narrowed channel (PNC) with a sub-distribution zone as a promising alternative for FC design. In addition, a modified volume of fluid (VOF) method is developed using an equivalent contact angle to represent the effect of the rough surface of gas diffusion layer (GDL) on water drainage. Then, a comparison among different FCs and design of structural parameters are conducted. The results show that the highest water drainage efficiency of 9.88 % ms−1 is achieved with the liquid removed in a film state at the pressure drop of 5.01 kPa. Considering the sub-distribution zone, the location and interval of baffles significantly affect water drainage efficiency, while the shape has minimal effect. The highest water drainage efficiency is observed when the baffles are located between the channels with an interval of 2 and 3 mm at low and high airflow inlet velocities, respectively. The PNC with a sub-distribution zone removes liquid rapidly at a moderate pressure drop, thereby reducing pumping losses and risks of membrane degradation.

Sound‐Based Assembly of Magnetically Actuated Soft Robots Toward Enhanced Release of Extracellular Vesicles

Magnetic soft robots have emerged as promising tools in biomedicine due to their wireless actuation, rapid response, and compatibility with biological systems. Despite the various innovative strategies proposed for their fabrication, they suffer from complex processes and limited cellular compatibility. Therefore, there is an urgent need to explore alternative approaches that are fast, mild, and highly tunable. Herein, a novel fabrication strategy for contactless assembly of soft‐robots is introduced for the first time. This technology exploits hydrodynamic instabilities at the free surface of a fluid layer, thus enabling the fabrication of centimeter‐scale robots featuring diverse structural properties. These features show a wide range of deformation modes in response to magnetic fields, including folding, bending, and expanding. Furthermore, the design and assembly of novel actuators with customized shapes as fish‐ and butterfly‐like structures is shown. The fabricated patterns exhibit different modes of motion under the influence of uniform magnetic fields. As a proof of concept, an innovative application of this technology combined with the proposed soft robots is represented by the enhanced release of extracellular vesicles. Altogether, this novel fabrication method along with the newly developed magnetic soft robots enables the manufacturing of high‐performance, multifunctional, and cytocompatible intelligent systems.

Surface layers formed upon chamber treatment of copper with octadecylamine

Surface layers formed upon chamber treatment of copper with octadecylamine

Ion incidence angle-dependent pattern formation on AZ® 4562 photoresist by reactive ion beam etching

Reactive ion beam etching is a key technology in the field of ultra-precise surface engineering. In this process nanopatterns can emerge and alter the functional properties of the surfaces. Therefore, it is necessary to understand which reactive ion beam parameters influence the emergence of these nanopatterns. In this study the influence of reactive ion beam etching on the commercially available photoresist AZ® 4562 is investigated. Atomic force microscopy and scanning electron microscopy reveal the formation of nanopatterns (ripples, triangular features, protrusions, facets) depending on a wide range of ion incidence angles (0°–75°) as well as the etch time. The emerged nanopatterns resemble those known from inorganic materials and therefore, lead to the assumption that local redeposition, surface viscous flow and dispersion plays an important role for the pattern formation on polymer surfaces. Major difference from ion beam erosion with inert species is the absence of nanoholes. Spectroscopic ellipsometry shows that the thickness of the modified surface layer depends on the ion incidence angle but not on the fluence in the investigated range. Using X-ray photoelectron spectroscopy, trends of the chemical composition of the surface/near-surface region were detected, which depend on ion incidence angle and etch time.

Investigation of mechanical and tribological properties of NiCrAlY/ZrO2-Y2O3 coatings obtained by detonation spraying

In this study, multilayer gradient NiCrAlY/ZrO2-Y2O3 coatings obtained by detonation spraying in 1D (spot sputtering) and 2D (full-surface scanning sputtering) modes were investigated. The structure of coatings was analyzed using scanning electron microscopy and electron dispersion analysis, mechanical properties (hard- ness, modulus of elasticity) were determined using various techniques. The tribological characteristics of the coatings including abrasion resistance and coefficient of friction were also studied. It was determined that the coatings consist of alternating layers of NiCrAlY and ZrO2-Y2O3, creating a multilayer gradient structure. It was found that the NiCrAlY layers act as a bonding element, providing interlayer adhesion, and the ceramic ZrO2-Y2O3 layer serves as a thermal barrier protecting the substrate from high temperature loads. It was found that the coatings in 2D mode have high microhardness compared to coatings in 1D mode. It was deter- mined that the hardness of coatings smoothly increases from the substrate to the surface layers due to the gra- dient increase in the content of ceramic materials. It was found that coatings obtained in 2D mode have better wear resistance and lower coefficient of friction compared to coatings in 1D mode, indicating the greater effi- ciency of coatings in dry friction conditions and their ability to prevent wear of the substrate material.

Effect of sulfur on synergistic corrosion behavior of Q235 and 16Mn steel in sodium aluminate solution

In this study, the corrosion electrochemistry and corrosion behavior of two steels were studied under the simulated alumina production conditions. The corrosion rate of 16Mn steel is greater than that of Q235 steel. The effect of S2− concentration on corrosion rate was significantly higher than that of S2O32−. The synergistic corrosion rates of Q235 and 16Mn steels increase at first and then decrease with the sulfur content, and the peak value appears when the concentration of S2− and S2O32− is 4 g/L and 3 g/L respectively. There are two main types of corrosion products: one is surface octahedral grain, which is composed of Fe2O3, Fe3O4 and Al2O3.The other is the interlayer corrosion between the surface layer and the matrix, which is composed of FeS, FeS2 and NaFeO2.The formation mechanism of the corrosion and corrosion mechanism were obtained by analyzing the phenomenon of ion competitive adsorption. Further validation and analysis of ion competition adsorption phenomenon were conducted using first-principles calculations based on density functional theory (DFT). The formation of corrosion products on the steel surface was investigated at an ion level, and the adsorption energies of OH− and S2− at the top site of Fe(110) surface were calculated. It was found that S2− is more likely to be adsorbed on the Fe(110) surface compared to OH−. The corrosion mechanism of steel is discussed preliminarily.

Fabrication of High-Performance Asphalt Mixture Using Waterborne Epoxy-Acrylate Resin Modified Emulsified Asphalt (WEREA)

Existing research shows that using waterborne epoxy resin (WER) instead of emulsified asphalt as the binder for cold mix asphalt (CMA) can enhance the rutting resistance, high-temperature performance, fracture performance, and early performance of CMA. In order to eliminate the potential drawbacks such as insufficient strength and low-temperature performance of CMA during application, a novel method was proposed in this study for the preparation of waterborne epoxy-acrylate resin (WER), specifically tailored to modify emulsified asphalt, resulting in waterborne epoxy-acrylate resin emulsified asphalt (WEREA). The modification effect of WER on emulsified asphalt was evaluated through rheological tests and direct tensile tests. A modified design method based on the conventional Marshall design method was proposed to determine the optimal mix proportions, including the key parameters of specimen compaction and curing. The results revealed that the incorporation of WER led to a substantial improvement in the complex shear modulus and a concurrent decrease in the phase angle. When the temperature exceeded 60 °C, the phase angle exhibited a diminishing trend, indicative of a reduced viscosity as temperatures escalated. As the WER content increased, a decrease in the direct tensile strain rate was observed, accompanied by a substantial elevation in direct tensile strength. At various stress levels, the shear strain of WEREA decreases with increased content of WER, indicating that the incorporation of WER can enhance the hardness of emulsified asphalt and improve its deformation resistance. The results from MSCR tests indicate that WER could significantly improve the elasticity and hardness of emulsified asphalt, transitioning it from a viscoelastic material to an elastic material, thereby improving its deformation resistance, resistance to rutting, and high-temperature performance. The results of fatigue life are consistent with those of the amplitude sweep, both reflecting the improvement of resistance to deformation of emulsified asphalt by WER. This indicates that WER has a significant improving effect on the fatigue resistance of emulsified asphalt. Furthermore, the Marshall design tests further confirmed the advantages of WEREA in asphalt mixtures. The optimal preparation for the WEREA mixture was proposed as follows: double-sided compaction for 50 times each, aging at 60 °C for 48 h, optimal moisture content of 5.14%, cement content of 2.5%, and emulsion content of 8.4%. The optimal mix proportions identified through these tests yielded asphalt mixtures with significantly improved stability, reduced flow value, and enhanced rutting resistance compared to the hot-mix asphalt mixture (HMA) of AC-16. These findings suggest that WEREA has the potential to significantly enhance the durability and longevity of asphalt pavements. For future applications, it can be explored for use in producing cold recycled asphalt mixtures. In addition to designing the WEREA mixture according to AC-16 gradation, consideration can also be given to using a gradation with a smaller nominal maximum aggregate size for the application in the surface layer or ultra-thin wearing course.

Experimental and modeling approaches to determine drug diffusion coefficients in artificial mucus

Asthma, usually characterized by inflammation and mucus accumulation, causes restricted airflow and impaired lung function. The physiological and biochemical characteristics of mucus pose a strong barrier for drugs administered orally or via the pulmonary route for asthma treatment. In this study, two drugs commonly employed in the treatment of asthma, theophylline and albuterol, were placed in contact with an artificial mucus layer, measuring their interface concentrations, and modeling the concentration profiles to determine their diffusion coefficients. To monitor the diffusion process, the upper surface of a mucus layer was placed in contact with the drug solutions and the lower mucus surface was in contact with a zinc selenide crystal to allow for time-resolved Fourier transform infrared spectroscopy (FTIR) measurements. FTIR spectra were collected at constant time intervals and monitored for quantitative changes in spectral peaks corresponding to functional groups specific to each of these drugs. Changes in peak heights were correlated to concentration via Beer's Law. Fick's 2nd Law of Diffusion was used along with Crank's trigonometric series solution for a planar semi-infinite sheet to analyze the concentration data and determine diffusion coefficients. Using this method, fitting the experimental data resulted in diffusivity coefficients of D = 6.56 x 10−6 cm2/s for theophylline and D = 4.66 x 10−6 cm2/s for albuterol through artificial mucus. The drug diffusivity coefficients align closely with literature reports, wherein, diffusivity data was obtained experimentally using a rotating-disk apparatus and intrinsic dissolution technique. By coupling analytical and experimentally determined drug diffusion data, this approach provides a fast, non-invasive method for quickly assessing drug diffusion profiles through complex media.

Swelling-assisted surface grafting strategy for multichannel antifouling membranes: Reconstruction of surface pore structure and applications in microalgae harvesting and blood purification

Membrane fouling remains a major challenge in membrane separation. The modification of hydrophilic membrane surfaces can mitigate irreversible fouling deposition, thereby improving antifouling properties. Effective surface modification strategies are essential techniques for developing highly efficient antifouling membranes. In this work, a swelling-assisted surface grafting strategy was proposed for multichannel antifouling membranes, where various lengths of polyvinylpyrrolidone (PVP) brushes were grafted on the surface of polysulfone membrane using reversible addition-fragmentation chain transfer polymerization. The successful grafting of PVP polymer brushes was confirmed using Fourier transform infrared spectrometer and X-ray Photoelectron Spectroscopy. Changes in membrane morphology and pore structure were observed via scanning electron microscope and atomic force microscope. During the grafting process, the amphiphilic macromolecules formed through grafting were selectively swelled by graft solvent, leading to the formation of mesopores in both the surface layer and sublayer of the membrane, which formed additional water transport channels. The introduction of hydrophilic polymer brushes and the change of pore structure significantly boosted the hydrophilicity and permeability of the membranes. As a result, the water contact angle decreased from 85° to 42°, accompanied by an approximate 3.24-fold increase in pure water flux (PWF). Due to superior hydrophilicity, modified membranes demonstrated exemplary performance in microalgae harvesting, boasting a microalgae retention rate nearing 100 % and low fouling resistance (2.12 × 1012 m−1). In algal filtration experiments, a confocal laser scanning microscope was employed to assess the activity of filtered algae on the membrane surface. The prepared membranes effectively maintained the bioactivity of algae while also achieving a high flux recovery rate (90.7 %) following filtration and cleaning. Furthermore, in blood cell compatibility tests, the modified membranes exhibited resistance to blood cell adhesion and sustained a low hemolysis rate (0.06 %). Overall, this strategy offers unique insights into the fabrication of antifouling surfaces and shows considerable promise for large-scale applications in microalgae harvesting and blood purification.

Experimental evaluation of multiple-component residual stress distribution in a dissimilar metal repair joint of ferritic/martensitic steel using the asymmetric-cut and the symmetric-cut contour method

A thick multi-pass butt-welded ferritic/martensitic steel (P91) joint is prepared and the local region of the weld is repaired with an ENiCrFe-3 nickel-based alloy using the manual metal arc welding method. The repair weld including part of the base metal is then subjected to ultrasonic impact treatment (UIT). A three-cut contour method, including two asymmetric cuts and one symmetric cut, is developed in the present study to obtain the two-dimensional residual stress distributions at different locations, and the stress release after multiple cuts is considered to get the original stress distribution before cuts. The measurement procedure is introduced in detail. The longitudinal stresses in the repair weld and the initial weld of the P91 steel joint, as well as the transverse stress at the weld center, are finally obtained. The effects of the dissimilar metal repair weld at the local region on the longitudinal and transverse welding residual stresses are investigated. In addition, the applicability of UIT to mitigate the surface stress in nickel-based alloy repair weld is analyzed. The results show that the transverse and longitudinal stresses in the nickel-based alloy repair weld are both tensile stresses, the maximum longitudinal stress is close to the yield strength of the B91 weld metal and occurs in the heat-affected zone of the repair weld located in the initial weld. Repair welding causes the internal transverse compressive stress region to be narrower than in the original weld. UIT can be used to introduce compressive stress to the surface layer of the nickel-based alloy repair weld.