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Abstract In many cases, due to high surface stress, stress concentration and wear, the metal material starts to fail from the surface. It is necessary to investigate interface evolution characteristics under high‐speed collisions for widely used metal materials. The microstructures and strengthening mechanism of the Ni balls after high‐speed collisions with 316 L stainless steel were investigated by a self‐designed high‐speed collisions test system. It was found that ultrafine twins and α'‐martensite were formed in 316 L stainless steel (316 L SS) near the interface region. The elongated nano/ultrafine lamellar structures with high‐angle grain boundaries in Ni ball were formed near central interface region, while more equiaxed nano/ultrafine grains with random orientations and high‐angle grain boundaries were formed near edge interface region due to friction process and high shear stress. The gradient structure in the Ni ball near central interface region was formed due to normal stress, while the high shear strain could promote the formation of finer equiaxed grains in the Ni ball near edge interface region. Moreover, in addition to grain refinement strengthening, nano/ultrafine lamellar structures with sufficient intragranular recrystallization facilitated the activation of more dislocations and increased the strengthening of the Ni ball near central interface region.

Large aggregate asphalt mixtures can absorb noise, reduce water damage, effectively improve the service life of roads, and reduce environmental pressure. In this study, the fatigue characteristics of a large-sized asphalt mixture, LSAM-30, were investigated using four-point bending tests. The fatigue performance of LSAM-30 was compared to that of AC-13 and AC-20 asphalt mixtures across a range of temperatures, frequencies, and strains. The results indicated that the temperature, frequency, and strain significantly affect the fatigue performance of LSAM-30. As the temperature or frequency increased, the disparity in the fatigue performances of LSAM-30, AC-13, and AC-20 became more pronounced. Furthermore, the variations in the strain did not exhibit a clear pattern in the fatigue performance ratio among the three asphalt mixtures, with the ratio changes being minor (<5%). Additionally, an exponential-function-based predictive equation was proposed, showing how the fatigue characteristics of LSAM-30 vary with changes in frequency and temperature. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of carbonation treatment on the rebound strength measurement curve of machine-made sand concrete, this study conducted research on the carbonation mechanism sand concrete rebound strength measurement curve through rebound and compressive strength tests using carbonation degree and concrete strength grade as control variables. The results showed that in the short aging period, carbonation treatment had little effect on the compressive strength of manufactured sand concrete but could cause an increase in the rebound value measured by the high-strength and heavy rebound hammers. As the strength grade of the manufactured sand concrete increased, the rebound value measured by both the high-strength and heavy rebound hammers increased accordingly. Compared with the high-strength rebound hammer, the heavy rebound hammer had higher accuracy in detecting the rebound of the carbonated manufactured sand concrete. This study established measurement curves for uncorrected and corrected carbonation depths, among which the accuracy of the corrected carbonation depth measurement curve was higher. At the same time, this measurement curve has been applied to the rebound test of the Pinglu Canal Extra-Large Bridge Project in Guangxi, China, and its practicality and reliability have been verified. [ABSTRACT FROM AUTHOR]

The pathogen SARS-CoV-2 binds to the receptor angiotensin-converting enzyme 2 (ACE2) of the target cells and then replicates itself through the host, eventually releasing free virus particles. After infection, the CD8 T-cell response is triggered and appears to play a critical role in the defense against virus infections. Infected cells and their activated CD8 T-cells can cause tissue damage. Here, we established a mathematical model of within-host SARS-CoV-2 infection that incorporates the receptor ACE2, the CD8 T-cell response, and the damaged tissues. According to this model, we can get the basic reproduction number R 0 and the immune reproduction number R 1. We provide the theoretical proof for the stability of the disease-free equilibrium, immune-inactivated equilibrium, and immune-activated equilibrium. Finally, our numerical simulations show that the time delay in CD8 T-cell production can induce complex dynamics such as stability switching. These results provide insights into the mechanisms of SARS-CoV-2 infection and may help in the development of effective drugs against COVID-19. [ABSTRACT FROM AUTHOR]

Surface molybdenum enrichment on 2205 duplex stainless steel was obtained by the ball milling technique. The electrochemical results showed molybdenum enrichment on the surface of 2205 duplex stainless steel improved its corrosion resistance in a typical proton exchange membrane fuel cell environment. This was mainly attributed to higher molybdenum content in the passive film formed on 2205 duplex stainless steel after ball milling. The decreased donor and acceptor concentrations improved significantly the corrosion resistance of surface molybdenum-enriched 2205 duplex stainless steel bipolar plates in the simulated cathodic proton exchange membrane fuel cells environment. In addition, the interfacial contact resistance of the 2205 duplex stainless steel bipolar plates slightly decreased due to surface molybdenum enrichment. Keywords: Surfaces, Structural materials, Microstructure, X-ray diffraction

The present work investigates the corrosion resistance of as-cast FeCoCrNiMn high-entropy alloy in borate buffer solution. Compared with 304 and 316L stainless steels steel, as-cast FeCoCrNiMn high-entropy alloy exhibited excellent passivation ability. This should be attributed to homogenization of alloying elements. Highly corrosion-resistant elements in as-cast FeCoCrNiMn alloys, for example, Cr, Co and Ni, could promote the formation of protective passive film in borate buffer solution. Moreover, combined effect of high mixing entropy and sluggish diffusion also could improve the corrosion resistance. The formation mechanism of the passive films on the surface of as-cast FeCoCrNiMn alloys satisfied the point defect model.

COVID-19, which broke out globally in 2019, is an infectious disease caused by a novel strain of coronavirus, and its spread is highly contagious and concealed. Environmental vectors play an important role in viral infection and transmission, which brings new difficulties and challenges to disease prevention and control. In this paper, a type of differential equation model is constructed according to the spreading functions and characteristics of exposed individuals and environmental vectors during the virus infection process. In the proposed model, five compartments were considered, namely, susceptible individuals, exposed individuals, infected individuals, recovered individuals, and environmental vectors (contaminated with free virus particles). In particular, the re-positive factor was taken into account (i.e., recovered individuals who have lost sufficient immune protection may still return to the exposed class). With the basic reproduction number R 0 of the model, the global stability of the disease-free equilibrium and uniform persistence of the model were completely analyzed. Furthermore, sufficient conditions for the global stability of the endemic equilibrium of the model were also given. Finally, the effective predictability of the model was tested by fitting COVID-19 data from Japan and Italy. [ABSTRACT FROM AUTHOR]

• Strain induced grain growth quickly consumes high-strain regions through grain boundaries. • Fine grains form from the uniform activation and growth of strain induced grain growth grains by grain boundaries. • Pre–existing twins facilitate GBs low-mobility GBs in tuning their configuration and local plasticity strain. A strain induced grain growth behaviour in laser powder bed fusion 316L austenitic stainless steel was investigated in this work. The intrinsic characteristics of the samples, such as crystallographic orientations, dislocation density, low angle grain boundaries and twins, were investigated via quasi–in–situ electron backscatter diffraction. Additionally, grain growth during plastic deformation in samples annealed at 800 °C was attributed to the combined influence of pre–existing twins and strain–induced grain boundary migration. [ABSTRACT FROM AUTHOR]

In order to explore the influence of water dilution on performance of Cr3+ polymer weak gel in porous medium, the performances of pure polymer solution and Cr3+ polymer weak gel were studied according to the laboratory testing of viscosity, micro-structure performances (polymer molecule aggregate dimension, polymer molecule aggregate configuration and Zeta potential), seepage characteristics and oil displacement effect under the condition of water dilution. The results indicated that, after diluting by water, pure polymer solution and Cr3+ polymer weak gel had an almost same viscosity, but there were obvious differences in micro-structure performance and seepage characteristics. Different with pure polymer solution, with the decrease of polymer concentration, on the one hand, the influence of free Cr3+ on electric double layer and shielding effect on electrostatic exclusion got weaker, on the other hand, water molecules were attracted by hydrophilic groups on the Cr3+ polymer weak gel molecular chains and then entered into the three-dimensional spatial structure of Cr3+ polymer weak gel, producing hydration and expansion. Therefore, the polymer molecule aggregate dimension of Cr3+ polymer weak gel presented a trend of continuous increasing. This characteristic was good for keeping the injection pressure at a higher value during diluting in the porous medium, which could be used to improve oil recovery in offshore oilfield through conducting injection of water-alternating- Cr3+ polymer weak gel. [ABSTRACT FROM AUTHOR]

Hierarchically porous P substituted HZSM‐5 (H[P, Al]‐ZSM‐5‐AT‐0.05 M) was successfully synthesized by isomorphous substitution method with introduced P atoms into ZSM‐5 zeolite frameworks followed by alkali treatment. H[P, Al]‐ZSM‐5‐AT‐0.05 M was characterized by XRD, ICP‐OES, SEM, FT‐IR, N2 adsorption‐desorption, NH3‐TPD, XPS, Py‐IR, and TG‐DTA, respectively. The surface area, pore volume, particle size and P/Al (molar ratio) are 328 m2.g−1, 0.23 cm3.g−1, 563 nm and 0.027, respectively. The catalytic performance of H[P, Al]‐ZSM‐5‐AT‐0.05 M in coupling reaction of methanol with 1‐butene was investigated in the fixed‐bed reactor. On the condition of reaction temperature at 500°C under atmosphere pressure, the main product is propylene with the selectivity and yield of 33.7% and 31.0%, respectively. Hydrogen transfer index was calculated to 0.24. Moreover, its diffusion limitation was investigated with the self‐etherification of benzyl alcohol reaction. The value of Thiele modulus (η) and effectiveness factor (ϕ) are 0.08 and 16.9, respectively. The scheme of isomorphously substituted method of introducing P into ZSM‐5 framework and catalytic performance over H[P, Al]‐ZSM‐5 and H[P, Al]‐ZSM‐5‐AT‐0.05 M in coupling methanol with 1‐butene. P substituted HZSM‐5 is treated with NaOH solution to form mesoporous zeolites. The result shows that H[P, Al]‐ZSM‐5‐AT‐0.05 M exhibited higher catalytic stability, higher apparent reaction rate, effectiveness factor and lower content of diffusion limitation in coupling of methanol with 1‐butene to propylene reaction. [ABSTRACT FROM AUTHOR]

Catalytic performance is influenced by the morphology and assembly of catalyst particles. Therefore, Zn ion‐doped HZSM‐5 zeolite with different morphological structures is prepared using post‐treatments of selective dissolution and recrystallization, causing silicon components to migrate from the interior to the exterior in the different template etching processes. The core–shell, hollow, and hierarchical core–shell Zn/HZSM‐5 microspheres with weak acid sites on the external surfaces are successfully synthesized. Hierarchical core–shell‐structured Zn/HZSM‐5 microspheres with a silicon‐rich surface layer are prepared using an etching method in n‐butylamine solution. Their catalytic activity is investigated in methanol aromatization. The functionalized morphological Zn/HZSM‐5 catalysts show good catalytic performance and the silicon‐rich surface layer improves selectivity of p‐xylene in the reaction of methanol to aromatics. Three morphological structured zeolite synthesis routes for p‐xylene are reported and selectivity is studied. Zn/HZSM‐5Si shows lower activity in the conversion of methanol to aromatics, but higher selectivity to xylene (particularly p‐xylene) considering benzene, toluene, and xylene. The Zn/HZSM‐5 catalysts treated in tetrapropylammonium hydroxide (TAPOH) and n‐butylamine solution exhibit excellent catalytic activity and stability in MTA reactions. [ABSTRACT FROM AUTHOR]

Many NiO platelets were formed on Ni foam after hydrothermal process, while flower-like NiO with many small mesoporous nanoflakes was obtained on the surface of graphene foam. Electrochemical results showed that the NiO/graphene composites exhibited very high specific capacitance 1062 F g −1 at 1 A g −1 and excellent cycling stability (90.6% capacitance retention after 5000 cycles at 1 A g −1 ). The promising NiO/graphene composites exhibited higher supercapacitor performance than NiO platelets on Ni foam. The excellent supercapacitor performance of the former should be attributed to the 3D graphene conductive network and the mesoporous NiO nanoflakes which promoted efficient charge transport and electrolyte diffusion. [ABSTRACT FROM AUTHOR]

Hydrothermal method is used to in situ synthesize mesoporous graphene@NiMoO4 nanocomposites as supercapacitor electrodes. NiMoO4 nanorods are formed on fresh graphene surface, while scattered NiMoO4 nanoparticles are obtained on the surface of ball milled graphene. graphene@NiMoO4 nanocomposites electrodes exhibit a higher electrochemical performance compared with a pure NiMoO4 electrode, and the ball milled graphene@NiMoO4 electrodes have the maximum specific capacitance of 2100 F g-1 at 1 A g-1 discharge current and maintains at least 92% of its initial capacitance after 5000 operational cycles. Such an enhanced supercapacitive performance originates from the mesoporous structure, more electroactive sites, large specific surface area, high electrical conductivity and synergistic effect between NiMoO4 and the graphene. [ABSTRACT FROM AUTHOR]

This paper presents an integrated processing method that applies principal component analysis (PCA), artificial neural network (ANN), information entropy and information fusion technique to analyze acoustic emission signals for identifying fatigue damage in a steel structure. Firstly, PCA is used to build different data spaces based on the damage patterns. Input information from each sensor is diagnosed locally through ANN in the data space. The output of the ANNs is used for basic probability assignment. Secondly, the first fusion operation adopts Dempster-Shafer (D-S) evidence theory to combine the basic probability assignment value of ANNs in the different data space of a sensor. Finally, the fusion results of each sensor are combined by D-S evidence theory for the second fusion operation. In this paper, information entropy is used to calculate the uncertainty and construct basic probability assignment function. The damage identification method is verified through four-point bending fatigue tests of Q345 steel. Validation results show that the damage identification method can reduce the uncertainty of the system and has a certain extent of fault tolerance. Compared with ANN and ANN combined with information fusion methods, the proposed method shows a higher fatigue damage identification accuracy and is a potential for fatigue damage identification. [ABSTRACT FROM AUTHOR]

Nanohole graphene oxide (NHGO) was obtained in a homogeneous aqueous mixture of graphene oxide (GO) and H 2 O 2 at 120 °C. Supercapacitors were fabricated as the electrode material by using NHGO. A specific capacitance of 240.1 F g −1 was obtained at a current density of 1 A g −1 in 6 m KOH electrolyte and specific capacitance remained 193.6 F g −1 at the current density of 20 A g −1 . This was attributed to reducing the inner space between the double-layers, enhanced ion diffusion and large specific surface area. Supercapacitor prepared with NHGO electrodes also exhibited an excellent cycle stability. [ABSTRACT FROM AUTHOR]

The effects of reduced graphene oxide and molybdenum in amorphous nickel–phosphorus as bipolar plates on corrosion resistance in proton exchange membrane fuel cell environment were investigated. The amorphous nickel–phosphorus, amorphous nickel–phosphorus with molybdenum and amorphous nickel–phosphorus with reduced graphene oxide were obtained by the electrodeposition technique from a nickel sulfate bath. The electrochemical studies showed that the molybdenum in amorphous nickel–phosphorus improved corrosion resistance in typical proton exchange membrane fuel cell environment. In addition, the amorphous nickel–phosphorus with reduced graphene oxide exhibited the best corrosion resistance in typical proton exchange membrane fuel cell environment. The synergistic combination of amorphous nickel–phosphorus and reduced graphene oxide could improve corrosion resistance, which was supported further by Mott–Schottky analysis. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effects of strain and heat treatment on strain-induced α′-martensite of AISI 304 stainless steel tubes were measured by X-ray diffraction. Moreover, the effects of strain and content of α′-martensite on passivated property on the surface of the material in borate buffer solution were evaluated by electrochemical technique. The results showed that the volume fraction of α′-martensite increased gradually with the increase of tensile strain for as-received and solid solution samples. However, α′-martensite in as-received sample was more than that in the solid solution sample. The electrochemical impedance spectroscopy results showed that the solid solution treatment improved corrosion resistance of the steel, especially for samples with small strain. Moreover, acceptor densities were always higher than donor densities for as-received and solid solution samples. With the increase of strain, the increase tendency of acceptor density was more significant than that of donor density. We also found that the total density of the acceptor and donor almost increased linearly with the increase of α′-martensite. The present results indicated that the increased acceptor density might lead to the decreased corrosion resistance of the steel. [Copyright &y& Elsevier]

In this study, we aimed to quantify the contribution of different transmission routes of the Middle East respiratory syndrome (MERS) and determine its transmissibility. Based on the natural history and transmission features of MERS in different countries, a susceptible-exposed-symptomatic-asymptomatic-recovered/death (SEIARD) model and a multi-route dynamic model (MMDM). The SEIARD model and MMDM were adopted to simulate MERS in South Korea and Saudi Arabia, respectively. Data on reported MERS cases in the two countries were obtained from the World Health Organization. Thereafter, the next generation matrix method was employed to derive the equation for the basic reproduction number (R 0), and the model fitting procedure was adopted to calculate the R 0 values corresponding to these different countries. In South Korea, 'Person-to-Person' transmission was identified as the main mode of MERS transmission in healthcare settings, while in Saudi Arabia, in addition to 'Person-to-Person' transmission, 'Host-to-Host' and 'Host-to-Person' transmission also occurred under certain scenarios, with camels being the main host. Further, the fitting results showed that the SEIARD model and MMDM fitted the data well. The mean R 0 value was 8.59 (95% confidence interval [CI]: 0–28.02) for MERS in South Korea, and for MERS in Saudi Arabia, it was 1.15 and 1.02 (95% CI: 0.86–1.44) for the 'Person-to-Person' and 'Camel-to-Camel' transmission routes, respectively. The SEIARD and MMDM model can be used to simulate the transmission of MERS in different countries. Additionally, in Saudi Arabia, the transmissibility of MERS was almost the same among hosts (camels) and humans. [ABSTRACT FROM AUTHOR]

Abstract: Effect of pre-deformation on corrosion behavior of AISI 304 stainless steel was investigated by electrochmeical measurements, and the influence factors were chacterized by microstructural analysis and electron backscattering diffraction (EBSD). The results of polarization curves and electrochemical impedance spectroscopy indicated that corrosion resistance decreased 15%-20% after 20% pre-deformation. The reason may be due to the martensite transformation and the pile-up of dislocation according to the change of the microstructure. EBSD displays that an increase in grain orientation of austensite and martensite is another factor leading to the decrease of corrosion resistance. Besides corrosion resistance can also be reduced by the increase of the variety and fractions of texture. While corrosion resistance increases because of the increase of low angle boundaries. [Copyright &y& Elsevier]

Nano‐grains on the surface region of the DZ125 directionally solidified nickel based superalloy is obtained through burnishing processing at both room and low temperature. Compared to the low temperature burnished (LTB) specimen, the {111}/[112] type nano‐twins are generated on the room temperature burnished specimen (specimen RTB). The results demonstrate that the nano‐grains could improve the corrosion resistance and promote the formation of compact corrosion product films on the burnished DZ125 alloy surface in a 3.5 wt% NaCl solution. The combined effects of local deformation nano‐twins and lower percentage of Cr2O3 in corrosion product film lead to the fact that the specimen RTB exhibits a relatively lower corrosion resistance compared to the specimen LTB. Nano‐grains are fabricated on the surface of DZ125 superalloy in this work. {111}/[112] type nano‐twins are found in room temperature burnished DZ125 superalloy. The corrosion resistance of DZ125 alloy is improved significantly after surface nanocrystallization. Nano‐grains without deformation nano‐twins induce the best corrosion resistance for DZ125 alloy. [ABSTRACT FROM AUTHOR]

A large number of pitting pits were formed on the surface of Ni foam by immersion corrosion in NaCl solution. The graphene was deposited on Ni foam templates, then 3D graphene foams were obtained by removing Ni foam in the mixed solution of ferric chloride and hydrochloric acid. It was found that pitting pits on Ni foam facilitated to form fewer-layers graphene, however, pitting pits on Ni foam induced more defects on 3D graphene foam. The graphene with fewer-layers exhibited better electrical and mechanical properties for strain sensor devices. Moreover, fewer-layers graphene effectively inhibited degradation of resistance during cycling stability tests. [ABSTRACT FROM AUTHOR]

The supercapacitor performances of MnO 2 , Co 3 O 4 nanowire and Co 3 O 4 @MnO 2 core-shell structure are compared, and optimized Co 3 O 4 @MnO 2 core-shell nanowire arrays present the highest specific capacitance of 1646 F g −1  at a current density of 1 A g −1 and lowest interfacial charge transfer resistance. The impedance spectroscopy clearly shows the MnO 2 nanosheets surrounding Co 3 O 4 nanowire play an important role in reducing the resistance. During the hydrothermal process, the concentration of KMnO 4 solution has a significant effect on the final morphology of Co 3 O 4 @MnO 2 core-shell structure which is controllable and shows quite different electrochemical property. The relationship between morphology and supercapacitor behavior is studied, and the optimal concentration of KMnO 4 solution is approximately 0.015 M. The pore size distribution shows that the sample synthesized in 0.015 M KMnO 4 solution has the highest percentage of relatively larger poles, which facilitate the electrolyte ion transfer. [ABSTRACT FROM AUTHOR]

Abstract In order to quantitatively study the matching between hydrophobically associating polymers (HAPs) and reservoir pore-throat size in offshore oilfields, the geological characteristics and fluid properties of the S area reservoir in the Bohai Oilfield were used as a research platform. After determining the matching of HAP solutions with different association degrees and core permeabilities using a seepage experiment at a constant flow rate, the matching between the diameter of the HAP aggregates (D h) and the median pore-throat radius was quantified by combining the relationship between core permeability and median pore-throat radius. Finally, the importance of matching on the oil displacement effect of the HAP solution was demonstrated using homogeneous cores and heterogeneous cores with separate injection and production interlayers. The results showed that the diameter of the HAP aggregates, as well as their morphology and ability to increase viscosity, were highly related to the association degree of HAP. As the association degree of HAP was varied, the matching between cores with different permeabilities and the beta-cyclodextrin (β-CD)/HAP compound systems also changed. Under the experimental conditions used in this study, the ratio between the median pore-throat radius and D h ranged from 4 to 7. During the process of HAP flooding, suitably increasing the D h , i.e., increasing the association degree between HAP molecules, could allow control of the mobility of the HAP solution. The oil displacement effect of HAP was closely related to the matching between the HAP and reservoir pore-throat, rather than the viscosity of the HAP solution. Good matching between the HAP and reservoir pore-throat not only achieves fluid diversion but can also expand the swept volume in the low-permeability layer to ensure good oil displacement ability. Highlights • As for HAP, the diameter of aggregates, morphology and ability to increase viscosity were highly related to the association degree of HAP. • The oil displacement effect of HAP was closely related to the compatibility between the HAP and reservoir pore-throat instead of the viscosity. • Well compatibility not only achieves fluid diversion but can also expand the swept volume in the low-permeability layer. [ABSTRACT FROM AUTHOR]

Coarsening of nanoscale (Ti,Mo)C precipitates within quasi-polygonal ferritic (QPF) matrix and polygonal ferritic (PF) matrix is studied via HRTEM and In-situ heating TEM. Influenced by different nucleation processes, inverse coarsening process showing dissolution of large clustered precipitates and growth of small interphase precipitates is directly observed in the PF matrix. However, due to the evolution of high-density subboundaries, coarsening of precipitates in QPF matrix is mainly characterized by the subboundary migration assisted coarsening process, during which arch-like coarsened precipitates form after the sweeping of subboundaries. Analysis of atomic structure clarify that “imposts” of the arch-like coarsened precipitates are established by the re-precipitation of solute atoms from movable subboundary to the close packed planes {111} of (Ti,Mo)C precipitates, and that the “key stones” are constructed due to the change of re-precipitation planes to {200}. Geometric phase analysis (GPA) illustrates that not only the change of re-precipitation direction during the formation of arch-like precipitates, but also the selective coarsening of clustered precipitates in PF matrix, is caused by the highly anisotropic strain field around (Ti,Mo)C precipitates. [ABSTRACT FROM AUTHOR]