Search

This study investigates a kind of masonry consisting of clay-fired brick (fc = 10 MPa; ρ = 1 . 38 g / cm 3 ) and mortar (fc = 10 MPa; ρ = 1 . 8 g / cm 3 ). Clay-fired brick masonry connotes a traditional construction material of old architecture and public buildings. We carried out penetration experiments in which four clay-fired brick walls employing two different patterns were subjected to impact from small high-speed projectile, i.e. 12.7 mm armor-piercing explosive incendiary projectile and material tests in which the static and dynamic compressive strengths of clay-fired brick and mortar were determined by quasi-static and SHPB (Split Hopkinson Pressure Bar) tests. The experimental data include hit and exit velocities, damage configuration of clay brick masonry and mechanical properties of material at low and high strain rates, though which influence of thickness and bonding patterns of wall on kinetic loss of bullet, the damage patterns of masonry observed experimentally and dynamic increase of material strengths are analyzed. To keep minimum boundary inconsistency with reality, full 3D detailed finite element model consisting of two different material is established. Sharing common nodes and employing automatic tiebreak contact are combined to reduce computational time usage of large-scale model. For description of clay-fired brick and mortar Riedel–Hiermaier–Thoma (RHT) material model is employed. Material parameter set is derived based on experimental data, available literature and engineering assumptions. The numerical simulations study the mesh resolution dependency of material model, reproduce the crucial phenomena of masonry in experiment acceptably and offer more time-resolved insight into motion of bullet in the process of penetration. The feasibility of means of constructing finite element model and applying RHT model to the masonry herein and analogous constructions is explored through numerical investigation.

Developing an electrically conductive and corrosion-resistant coating is essential for metal bipolar plates of polymer electrolyte membrane fuel cells (PEMFCs). Although enhanced corrosion resistance was seen for Cr coated stainless steel (Cr/SS) bipolar plates, they experience a quick decrease of through-plane electrical conductivity due to the formation of a porous and low-conductive corrosion product layer at the plate surface, thus leading to an increase in interfacial contact resistance (ICR). To tackle this issue, the multilayer Cr coatings were deposited using the magnetron sputtering with a remote inductively coupled oxygen plasma (O-ICP) in the present study. After the O-ICP treatment, a Cr oxide layer (CrO*) is formed on the specimen surface. The CrO*/Cr/SS has a remarkably lower stable corrosion rate (iss) than that of the native Cr oxides (CrOn/Cr/SS). Compared with CrOn/Cr/SS, the excellent performance of CrO*/Cr/SS is attributed to a denser and thicker surface layer of CrO* with Cr being oxidized to its highest valence state, Cr (VI). More importantly, the through-plane electrical conductivity of the specimens treated by the optimized O-ICP decreases much slowly than CrOn/Cr/SS and thus, the increament of ICR of CrO*/Cr/SS after the potentiostatic polarization test is considerably smaller than that of CrOn/Cr/SS, which is benefited from the reduced iss that mitigates the deposition of corrosion products and hinders further oxidation of Cr coating. Therefore, CrO*/Cr/SS proves to be a well balanced trade-off between corrosion resistance and through-plane electrical conductivity. The results of this study demonstrate that O-ICP treatment on a conductive metal coating is an effective strategy to improve the corrosion resistance and suppress the increase of ICR over the long-term polarization. The technique reported herein exhibits its promising potential application in preparing corrosion resistant and electrically conductive coatings on metal bipolar plates to be used in PEMFCs.

Developing a high electrically conductive and corrosion-resistant coating on metal bipolar plate is of prime importance for its application in polymer electrolyte membrane fuel cells. To achieve it and further improve its through-plane conductivity, we herein prepared a composite coating by introducing Au microdots onto TiN coated stainless steel (Au/TiN/SS). Au dots provide additional conduction paths and thus Au/TiN/SS exhibits a remarkably lower interfacial contact resistance than that of TiN/SS after 200 h of test, suggesting that incorporation of Au dots into TiN provides an effective approach to achieving dual merits of high conductivity and corrosion resistance.

Most of nanoparticles catalyst for hydrogen evolution reactions (HER) exhibit low electrocatalytic activity due to the use of binders. Considering the synergistic effect of high activity of NiCoP and good conductivity of the nanoporous copper (NPC), and we report self-supporting NiCoP/NPC composites by electrochemical depositing NiCoP micro-spheres on NPC. The NPC substrate leads to the uniform nucleation of NiCoP micro-spheres and the high resistance against aggregation. As a result, the cost-effective NiCoP/NPC composites possess promising HER performance, with a low overpotential of 80 mV at 10 mA cm−2 and Tafel slop of 48.9 mV dec−1 in 1 M KOH.

Computational fluid dynamics (CFD) model of coal combustion is coupled with the one-dimensional hydrodynamic model of supercritical steam, and applied in the simulation of the superheater. The convective heat exchangers are neglected. Complex tube arrangements can be modeled with the aid of AutoCAD, and therefore the simulation could offer detailed information on heat exchangers. It is found that the outlet steam temperature of the tube is very sensitive to the variation of ash deposit temperature. Therefore it is not reasonable to use decoupled method for predicting the energy flux transported to the steam. The outlet steam temperature of a row of tubes is compared with the running data from the power plant. The simulation result fits well with running data. Nevertheless, one can impose an average steam temperature plus 50 K as the tube outside surface temperature; then calculates the temperature of the ash deposit according to the thermal resistance of ash deposit and energy flux. The result from this “simplified” coupled method is very close to fully coupled method.

Purpose The design and retrofit of the heat exchangers in a boiler should take into account the processes occurring on the side of combustion and steam. For this reason, this study aims to couple a one-dimensional hydrodynamic model of steam with computational fluid dynamics (CFD) simulation of flue gas. Design/methodology/approach Radiant/semi-radiant platen heat exchangers are simplified as plane surfaces for CFD, while convective heat exchangers are introduced into the CFD simulation as energy/momentum absorption sources. Findings Numerical simulation is performed for a 1,000 MWe coal-fired ultra-supercritical boiler. The calculation results are validated by the thermodynamic design data. Tube outside surface temperature, as well as ash deposit temperature distributions, are obtained. Originality/value Complex tube arrangements can be completed with the aid of AutoCAD, and therefore, the simulation could offer detailed information of heat exchangers. In a word, a more reliable modeling of the whole steam generation process is achieved.

To identify relationships among entities in natural language texts, extraction of entity relationships technically provides a fundamental support for knowledge graph, intelligent information retrieval, and semantic analysis, promotes the construction of knowledge bases, and improves efficiency of searching and semantic analysis. Traditional methods of relationship extraction, either those proposed at the earlier times or those based on traditional machine learning and deep learning, have focused on keeping relationships and entities in their own silos: extracting relationships and entities are conducted in steps before obtaining the mappings. To address this problem, a novel Chinese relationship extraction method is proposed in this paper. Firstly, the triple is treated as an entity relation chain and can identify the entity before the relationship and predict its corresponding relationship and the entity after the relationship. Secondly, the Joint Extraction of Entity Mentions and Relations model is based on the Bidirectional Long Short-Term Memory and Maximum Entropy Markov Model (Bi-MEMM). Experimental results indicate that the proposed model can achieve a precision of 79.2% which is much higher than that of traditional models.

The sign cancellation between scattering amplitudes makes fermions different from bosons. We systematically investigate Feynman diagrams' fermionic sign structure in a representative many-fermion system---a uniform Fermi gas with Yukawa interaction. We analyze the role of the crossing symmetry and the global gauge symmetry in the fermionic sign cancellation. The symmetry arguments are then used to identify the sign-canceled groups of diagrams. Sign-structure analysis has two applications. Numerically, it leads to a cluster diagrammatic Monte Carlo algorithm for fast diagram evaluations. The new algorithm is about $10^5$ times faster than the conventional approaches in the sixth order. Furthermore, our analysis provides important hints in constructing the relevant effective field theory for many-fermion systems.

${\mathrm{TaAs}}_{2}$ and ${\mathrm{NbAs}}_{2}$ are members of the ${MPn}_{2}$ family with weak topological invariants of ${Z}_{2}$ = [0;111]. Here, we report the tip-induced superconductivity achieved on both materials using the point-contact technique. Although the weak ${Z}_{2}$ number leads to strongly crystal-orientation-dependent surface states, we observed a universal relationship between the zero-temperature upper critical field ${H}_{c2}(0)$ and the critical temperature ${T}_{c}$ for different crystal orientations. Combined with first-principles calculations, the findings here could identify a bulk band, instead of the much speculated surface bands, playing the dominant role in the induced superconductivity. These results predict a great possibility to realize superconductivity in other members of the ${MPn}_{2}$ family possessing similar band structures and provide clues to understand the mechanism of tip-induced superconductivity.

This work investigates the effects of hydrogen and stress on the electrochemical and passivation behaviour of 304 stainless steel in 0.5 M sulfuric acid with 2 ppm sodium fluoride. Three major results are revealed: hydrogen and stress significantly increase the critical current density (icrit) and passive current density (ipass); hydrogen has a more obvious impact on icrit than that on ipass; a high synergistic effect between hydrogen and stress on current densities is observed at the intermediate hydrogen charging current densities range.

Tip-induced superconductivity at point contacts on the nonsuperconducting Weyl semimetal TaAs has been reported recently. Meanwhile, both the main tetragonal phase and the intergrown hexagonal phase of TaAs were identified to be topologically nontrivial according to theoretical calculations. Here, we report the observation of two independent local superconducting states induced at the point contacts formed on TaAs, which exhibit distinct temperature dependencies of the critical magnetic field ${H}_{c2}(T)$. A universal relationship between ${H}_{c2}(0)$, ${T}_{c}$, and the Fermi velocities of bulk bands near Weyl points of the two TaAs phases was uncovered, demonstrating the dominant role of the bulk bands in the emergence of superconductivity, rather than the surface states. These results provide a direction to study the mechanism of the tip-induced superconductivity in topological semimetals.

For precipitation-strengthened heat-resistant steels, property degradation resulted from phase coarsening is always one of the most critical challenges, and therefore, knowledge regarding the long-term influence of temperature on mechanical properties and microstructure is prerequisite for their applications. In this work, long-term thermal aging up to 10,000 h of typical alumina-forming austenitic (AFA) stainless steels was conducted, and evolution of microstructure and mechanical properties of these promising heat-resistant alloys were studied systematically. It was found that mechanical performance of the steel strengthened by secondary nanosized NbC showed not only much enhanced creep resistance, superior to that of most traditional heat-resistant steels, but also stable high-temperature strength even after long-term aging. The spheroidal secondary NbC particles showed extreme coarsening resistance with a low coarsening kinetic constant (almost six orders of magnitude smaller than that of the Laves Fe2Nb phase). The low interfacial energy of nanosize NbC, which was resulted from the cube-on-cube orientation relationship and semi-coherent interfacial structure with the matrix, gave rise to its sluggish coarsening kinetics. Our current findings not only confirm that the AFA alloys strengthened by dense precipitated, nanosized semi-coherent NbC is a promising structural material for long-term high-temperature applications, but also sheds new insights into understanding precipitation hardening mechanism for high-temperature materials in general.

Developing a corrosion-resistant and electrically conductive coating on metallic bipolar plates is essential to mitigate the performance degradation induced by the high cathodic transient potentials (CTPs) in the start-up/shut-down (SU/SD) processes of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a zirconium oxynitride (Zr2N2O) coating prepared by atomic layer deposition was used to improve the corrosion resistance of 304 stainless steel (304 SS) toward anodic dissolution at various CTPs. Triangular potential pulses were applied to the specimens to simulate potential variations at the cathode side of the PEMFCs at SU/SD stages. Results show that the Zr2N2O coating can provide effective protection at a CTP as positive as 1.1 V versus Ag/AgCl. At all CTPs examined, the peak current density ( ipeak) extracted from the pulse test of the coated specimen (Zr2N2O/SS) is 2 orders of magnitude lower than that of uncoated 304 SS, indicating that the presence of the Zr2N2O coating remarkably increases the corrosion resistance for the anodic dissolution induced by CTPs. More importantly, upon increasing the CTPs, 304 SS experiences severe intergranular corrosion after 4050 pulses, whereas Zr2N2O/SS shows slight pitting corrosion. The quite low ipeak and the mitigated corrosion morphologies of Zr2N2O/SS confirm that incorporating oxygen into the protective coating for achieving a high oxidation resistance is a feasible way to restrain the anodic dissolution caused by high CTPs. Analysis of the electron energy level diagrams of the passive film suggests a protective coating with a wider valence band contributing to the improved corrosion resistance toward the transpassive dissolution.

Susceptibility to corrosion of metal bipolar plates limits their application in polymer electrolyte membrane fuel cells (PEMFCs) and hence, the development of a conductive coating with high corrosion resistance is essential. Zirconium nitride (ZrN) exhibits high corrosion resistance but the interfacial contact resistance (ICR) after the long-term test is not satisfied owing to the surface oxidation and the corrosion products. To further improve the corrosion resistance and retain a considerable electrical conductivity, herein, we present a novel zirconium oxynitride (Zr2N2O) coating on 304 stainless steel by incorporating a controlled amount of oxygen into ZrN with plasma enhanced atomic layer deposition. The corrosion current density of the Zr2N2O coated specimen is found to be over one order of magnitude lower than that of the ZrN coated substrate. More importantly, after the long-term test, the ICR of Zr2N2O coated specimen is much smaller than that of ZrN coated specimen owing to the improved oxidation resistance and decreased corrosion rate, suggesting incorporating a controlled amount of oxygen into conductive coating is a feasible strategy to achieve an ultrahigh corrosion resistance while retaining a considerable electrical conductivity.

Glass-forming ability (GFA) is one of critical scientific problems for the field of bulk metallic glass (BMGs), and how to facilitate glass formation is always a central yet important research theme for this field. Compared with conventional BMGs in the same alloy system, newly developed high-entropy BMGs (HE-BMG) usually show much enhanced thermal stability, but appreciably reduced GFA. In contrast to the conventional wisdom, we found that GFA of the Zr20Cu20Hf20Ti20Ni20 HE-BMG could be enhanced by oxygen microalloying. The underlying mechanism was explored from both thermodynamic and kinetic point of view, and our analysis indicates that the high packing density resulted from addition of small oxygen atoms is responsible for the beneficial effect of oxygen. The current findings not only shed new insights into understanding of glass formation, but also broaden the view for exploring new kinds of HE-BMGs with enhanced properties and low manufacturing costs.

It is generally accepted that good glass formers have a high thermal stability against crystallization upon heating. In this paper, we report an unusual relationship between thermal stability and glass-forming ability (GFA) for high-entropy bulk metallic glasses (HE-BMGs). As compared with their conventional counterparts in the same alloy system, the HE-BMGs have a lower energy barrier for atomic diffusion during undercooling, which facilitates crystallization and then reduces the GFA. Our results clearly demonstrate that the GFA of BMGs is governed by the kinetics of the undercooled liquid, whilst their thermal stability is controlled by atomic diffusion in the glass-transition regime.

Electrochemical reduction of CO2 (CO2RR) holds the potential to battle the greenhouse effect through the synthesis of carbon-neutral fuels. The high efficiency of noble metal catalysts for CO2RR is, therefore, highly desirable to reduce the quantities of noble metals. We herein synthesized 5-fold twinned Ag nanowires (NWs) with diameters less than 25 (D-25) and 100 nm (D-100) through a facile bromide-mediated polyol method and subsequently, investigated their structure-driven enhanced catalytic activity for CO2RR. Compared with D-100 Ag NWs and Ag nanoparticles (NPs), D-25 Ag NWs possess remarkably enhanced current density ( j ) , together with significantly increased Faraday efficiencies (FEs) and energy efficiencies (EEs) over a broad potential range and achieve their maximum values of 99.3% and 61.3%, respectively. More importantly, a quite low onset overpotential (η) to initiate CO2RR and a stability with negligible degradation of over 24 h were obtained, further verifying the superior performance of D-25 Ag NWs for CO2RR. Density functional theory (DFT) calculations reveal that the improved catalytic activity over the ultrathin 5-fold twinned Ag NWs originates from the increased ratio of the catalytically active sites contributed by both diameter and length effects, and the special 5-fold twinned nanostructure completely enclosed by energetically favorable facets for CO2RR.

Influence of four types of potential polarization on the interfacial contact resistance (ICR) of Au/TiN coated 316 L SS bipolar plates used in polymer electrolyte membrane fuel cells is investigated. Au/TiN coating gives superior small ICRs under single potentiostatic or cyclic potentiodynamic polarization, demonstrating great potential for commercial application. However, cyclic combined polarization induces significant delamination of Au dots, and thus Au/TiN/SS exhibits a remarkable increase of ICR. Analysis of ICR and its dependence on Au dots suggest that 4–6% of Au surface coverage is the critical threshold value for Au/TiN coated metal bipolar plates to achieve the target of ICR.

Due to excellent energy absorption efficiency under bending collapse, multi-cell beams are extensively used as the components of protection structures. However, the theoretical prediction of their responses is still an unsolved problem. In this paper, two methods: dimensionless analysis method and energy analysis method are employed to derive the bending moment response of multi-cell tubes. Numerical simulations of double-cell tubes with different section dimensions are conducted first. The dimensionless analysis method is then employed to correlate the bending moment of double-cell tubes with the ratio of width to thickness b/t, the flow stress and the bending rotation angle. Based on Kecman's model, a theoretical model of double-cell tubes is presented and the bending moment response is derived according to the energy equilibrium of the system. Finally, the expression of a rolling radius of plastic hinge lines in the energy analysis method is determined to bridge the two methods. A comparison shows that the predictions provided by the present two methods agree well with the numerical results. Quadruple-cell tubes are also employed to validate the present methods and results show that the present methods are applicable for multi-cell tubes with other cross-sections.

A hash service environment containing H2S and CO2 in oil industry usually causes corrosion of carbon steel. In this study, the chromized coatings with different deposited time were prepared on the surface of carbon steel by the method of pack cementation to enhance its corrosion resistance. Then the microstructure, hardness, corrosion resistance as well as the semiconductor behavior of coatings in the simulated solution with saturated H2S and CO2 were investigated. The results show that the content of Cr in coating was increased by prolonging deposited time, and both chromium carbides and chromium nitrides were formed. Furthermore, coatings display higher polarization resistance, Rp, than that of the substrate, indicating a higher resistance to charge transfer on coating surface. The corrosion rates of coatings with different deposited time were significantly lower than that of substrate. Chemical analysis showed the formation of heavy sulfides on the surface of substrates after corrosion, while the least corrosion products were detected on the surface of coating with deposited time of 12 h. Mott-Schottky results indicated that coating of 12 h displayed less defects than the other two coatings with deposited time of 4 h and 8 h, which will be beneficial to improve corrosion resistance. The investigation showed that chromized coatings exhibited high corrosion resistance and owned a potential application in oil industry for corrosion prevention.

A flexible and self-healing supercapacitor with high energy density in low temperature operation was fabricated using a combination of biochar-based composite electrodes and a polyampholyte hydrogel electrolyte. Polyampholytes, a novel class of tough hydrogel, provide self-healing ability and mechanical flexibility, as well as low temperature operation for the aqueous electrolyte. Biochar is a carbon material produced from the low-temperature pyrolysis of biological wastes; the incorporation of reduced graphene oxide conferred mechanical integrity and electrical conductivity and hence the electrodes are called biochar-reduced-graphene-oxide (BC-RGO) electrodes. The fabricated supercapacitor showed high energy density of 30 Wh/kg with ~90% capacitance retention after 5000 charge–discharge cycles at room temperature at a power density of 50 W/kg. At −30 °C, the supercapacitor exhibited an energy density of 10.5 Wh/kg at a power density of 500 W/kg. The mechanism of the low-temperature performance excellence is likely to be associated with the concept of non-freezable water near the hydrophilic polymer chains, which can motivate future researches on the phase behaviour of water near polyampholyte chains. We conclude that the combination of the BC-RGO electrode and the polyampholyte hydrogel electrolyte is promising for supercapacitors for flexible electronics and for low temperature environments.

In this study, a duplex Ni P with yttria-fully stabilised zirconia (YSZ) nanoparticle composite coating was prepared by electroless deposition on a carbon steel substrate. The characteristics of the coatings were evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical and corrosion behaviour of the coating in a 3.5 wt.% NaCl solution was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). In addition, the effects of the YSZ nanoparticle concentration on the properties of the coatings were also discussed. The results show that the structures of the as-deposited duplex Ni-P-YSZ/Ni-P coating are amorphous, and it changes to a crystalline state after heat treatment. The surface roughness and morphology of the coating are affected by the addition of YSZ nanoparticles. The duplex coating exhibits both good microhardness and wear resistance as well as excellent corrosion resistance because of its special duplex structure.

Sudden environmental perturbations may affect the positivity of the solution of the susceptible-infected-recovered-susceptible (SIRS) model. Most of the SIRS epidemic models have no analytical solution. Thus, in order to find the appropriate solution, the numerical technique becomes more essential for us to solve the dynamic behavior of epidemics. In this paper, we are concerned with the positivity of the numerical solution of a stochastic SIRS epidemic model. A new numerical method that is the balanced implicit method (BIM) is set, which preserves the positivity under given conditions. The BIM method can maintain positive numerical solution. An illustrative numerical instance is presented for the numerical BIM of the stochastic SIRS model.

The forming of high-density tungsten-based alloys with large-scale complex structures and thin-plate structures has always been an unresolved problem. However, in this paper, the problem has been well solved by adopting a specific process strategy via selective laser melting. Through special scanning strategy, supporting structure and specific annealing process, a 55 × 55 × 0.4 mm thin plate structure was formed. The microstructure characterization, XRD results to calculate the elastic constant and actual experimental verification confirmed that the alloy hardly appeared macro or micro cracks. Furthermore, the addition of tantalum was helpful for the improvement of plasticity and the high-quality forming of refractory tungsten-based alloys. Meanwhile, it maintained high density, hardness and strength, which had great value for the application of high-density tungsten-based alloys.

The effect of Fe addition on the structure, mechanical and wear properties of Zr–Cu–Ni–Al bulk metallic glasses (BMGs) was systematically investigated by thermal analysis, transmission electron microscopy (TEM), the compression test, the pin-on-disk macroscopic wear test and the microscopic nanoscratch test. TEM observation revealed the formation of a second glassy phase with a few nanometers in diameter in the Zr63.6-xCu18Ni10.4Al8Fex (x = 1, 3, 5) BMGs. The results of the mechanical tests showed that although compression strength and hardness do not change much, a remarkable enhancement in plasticity occurs in the Zr58.6Cu18Ni10.4Al8Fe5 BMG, which is presumably due to the restriction of the nano-scale second phase on shear banding. Phase separation was also found to promote multiple shear bands, enhanced toughness and oxidative wear, which work synergistically during the tribological test to improve the wear resistance of Zr–Cu–Ni–Al BMGs. These findings provide some insights into the wear mechanisms of dual-phase BMGs, which may offer new strategies for design and optimization of BMGs with desired wear performance.

The bending resistance of multi-cell square tubes under three-point bending is investigated in this study. Partition plates are introduced in longitudinal direction and cross-section of square tubes to form multi-cell structures. Numerical simulation of the three-point bending test is carried out by nonlinear finite element code and experimental test is conducted to validate the numerical model. Parametric studies are then performed to investigate the influence of the number of cells, load conditions and other geometrical configurations on the bending resistance. Results reveal that the number of partition plates has important influence on the bending resistance of the structure and more partition plates do not necessarily lead to high energy absorption efficiency. The optimum configurations of the structures are found out and some valuable suggestions are offered for multi-cell structures under transverse loading.

In this paper, crack growth behaviour and the crack tip chemistry of X70 pipeline steel in the near-neutral pH environment were investigated using the in-situ measurements. The stress corrosion crack propagated forward under the cyclic load, with a mean crack growth rate (CGR) of 4.28 × 10–3 mm/cycle. The CGR da/dN obeys well with the stress corrosion fatigue mechanism. During the crack propagation, the crack tip environment differed significantly from the bulk solution. An aggressive electrolyte with low pH (about 4.0) and high concentration of Cl– (about 3.8 M) was produced near the crack tip. These results provided the direct evidence for simulating the crack tip solution and investigating the crack tip anodic dissolution.

Ni–Cr–Mo coating was prepared by a high power diode laser (HPDL) on X70 steel substrate (X70). In order to widen the application of this coating in oil industry, its surface morphology and corrosion behavior in simulated solutions separately with CO2, H2S as well as a mixed gas of them were studied and compared with those of X70 and 316 stainless steel (316 SS). The results show that X70 and 316 SS display inclusions on the surface before corrosion, while Ni–Cr–Mo coating exhibits a uniform and compact microstructure. Moreover, Ni–Cr–Mo coating has no change in morphology after corrosion, while X70 and 316 SS display severe corrosion and pitting corrosion, respectively. For each simulated solution, Ni–Cr–Mo coating exhibits higher corrosion resistance than X70 and 316 SS. Also, it shows higher polarization resistance than 316 SS and X70 as immersion time lasts, revealing an enhanced and stable anticorrosion performance. Furthermore, the variation trends of electrochemical response was opposite for X70 and 316 SS/Ni–Cr–Mo coating in simulated solutions with CO2, H2S as well as the mixed gas accordingly, which is caused by different corrosion mechanisms.

The susceptibility to stress corrosion cracking (SCC) of X70 pipeline steel under cathodic protection in near-neutral pH and acidic solutions was investigated by slow-strain-rate tensile test, circumferential-notch tensile (CNT) test, and three-point-bending (TPB) test. Results confirmed the existence of a hydrogen-induced plasticity (HIP) effect within a particular range of cathodic potentials. HIP effect lowered the SCC risk of X70 steel by releasing stress concentration at crack-initiation spots and then decreasing the stress intensity. Crack-growth behavior examined by CNT and TPB tests proved the existence of an HIP effect.

The CoNi equiatomic alloy was undercooled and spontaneously solidified using the glass fluxing method. The dendrite growth behaviors were recorded by a high-speed high-resolution camera. Three dendrite growth stages (i.e., the power law growth stage when undercooling ΔT 135 K) were found and well predicted by a dendrite growth model. For the as-solidified microstructures, the average grain size increases with undercooling, indicating that unique grain “coarsening” instead of common spontaneous grain refinement occurs. Such a grain “coarsening” phenomenon was ascribed to stress accumulation upon rapid solidification. Furthermore, a plenty of sub-grains were observed within the abnormal coarse grains. From the electron back-scattering diffraction results, the angle difference between neighbouring sub-grains was less than 6°. The current work might be helpful for not only theoretically understanding dendrite growth but also practically controlling the non-equilibrium microstructures.

High-performance light absorption devices have previously been obtained by coupling photons to conduction electrons. However, energy harvesting is limited in these devices because they only absorb light from one incident direction. We have developed a wide-band bidirectional visible light absorber (BLA) based on a quasi-periodic nanocone array coated with a dielectric-loaded Au monolayer. The proposed BLA is capable of simultaneously absorbing light from both the front and rear surfaces, yielding an average front absorption of 87.4% and a corresponding rear absorptivity of 76.2% in the range 300–700 nm. The bidirectional absorption properties were obtained at incident angles varying from 0 to 60°. Experimental and theoretical analyses indicate that these absorption properties can be ascribed to a combination of the localized cavity resonant mode, the localized surface plasmonic mode, the guided mode resonance, and hybrid coupling between the cavity resonant mode and the surface plasmonic mode. This concept provides a new pathway for the fabrication of new types of flexible or wearable solar thermoelectric devices, photodetectors, or other solid-state devices with large areas.

We report the observation of local superconductivity induced at the point contact formed between a normal metal tip and WC -- a triple point topological semimetal with super hardness. Remarkably, the maximum critical temperature is up to near 12 K but insensitive to the tip's magnetism. The lateral dimensions of the superconducting puddles were evaluated and the temperature dependencies of superconducting gap and upper critical field were also obtained. These results put constraints on the explanation of the induced superconductivity and pave a pathway for exploring topological superconductivity., Comment: 7 pages, 6 figures

In this study we examined the linear decomposition and relationship between the SMAP observed Polarization Ratio into surface soil moisture and vegetation. Temporal linear regression, per each SMAP pixel, is performed to estimate the decomposition coefficients. Variances (explained variance) in PR is predominantly dominated by dynamics of surface soil moisture and degrades with increasing vegetation amount. Although PR, by itself, is high in arid and semi-arid regions, due to lack of moisture and vegetation dynamics, the explained variance is very small.

A new photon-in/photon-out endstation at beamline 02B02 of the Shanghai Synchrotron Radiation Facility for studying the electronic structure of energy materials has been constructed and fully opened to users. The endstation has the capability to perform soft x-ray absorption spectroscopy in total electron yield and total fluorescence yield modes simultaneously. The photon energy ranges from 40 eV to 2000 eV covering the K-edge of most low Z-elements and the L-edge of 3d transition-metals. The new self-designed channeltron detector allows us to achieve good fluorescence signals at the low photon flux. In addition, we synchronously collect the signals of a standard reference sample and a gold mesh on the upstream to calibrate the photon energy and monitor the beam fluctuation, respectively. In order to cross the pressure gap, in situ gas and liquid cells for soft x-ray absorption spectroscopy are developed to study the samples under realistic working conditions.

Electrochemical CO2 reduction reaction (CO2RR) is a sustainable approach to producing carbon-neutral fuels when combined with renewable energies. Besides the emphatic consideration of developing efficient catalysts, a suitable conductive carbon agent served as co-catalyst with a low activity toward the competitive hydrogen evolution reaction (HER), is also highly needed. However, there have been limited studies focused on the investigation of co-catalyst during CO2RR, especially on their HER behavior. We herein explored the HER of various co-catalyst, i.e., acetylene black (AB), carbon black (CB) and graphite flake (GF) as well as carbon nanotube (CNT), and their composites with sub-25 nm Ag nanowires (NWs) as catalysts. GF and CB exhibit a higher activity toward CO2RR and HER, respectively. In contrast, CB/Ag NWs achieve the highest Faraday efficiency and partial current density for CO2RR, whereas CNT/Ag NWs prefer HER. The differences in HER suggest a critical influence of co-catalyst and this study points to a better guidance on the selection of co-catalyst for CO2RR. Keywords: Carbon dioxide reduction reaction, Hydrogen evolution reaction, Carbon support material, Ag nanowires

Bulk metallic glasses (BMGs) are potential candidate materials for numerous structural applications. However, this class of materials has a major limitation for engineering applications due to their inferior resistance to fatigue wear. In present work, a novel micro-scale repetitive impact test was utilized for fatigue testing of ZrCu-based BMGs (Zr63.6-xCu18Ni10.4Al8Fex, x = 0, 3, 5 at.%), and specific attention was paid to the micro-alloying effect on wear resistance. Transmission electron microscopy of as-cast Zr58.6Cu18Ni10.4Al8Fe5 revealed amorphous structure with the formation of a second glassy phase of few nanometers in diameter. Although these structural changes have minor effects on hardness and modulus, they have a substantial influence on fatigue wear resistance. Phase separation was found to promote numerous shear bands, which induced strain hardening, and improved the crack resistance. Consequently, all these features are considered to contribute the improved wear resistance. On the contrary, a monolithic glass without Fe addition lacks any microstructural features that can provide means for the local arrest of shear bands and incipient fatigue cracks. These findings improve the understanding of the impact fatigue mechanisms and provide suggestions for the future design of BMGs with excellent wear performance.

We propose a hierarchy set of minimal optical Raman lattice schemes toward the experimental realization of spin-orbit (SO) couplings of various types for ultracold atoms, including two-dimensional (2D) Dirac type of $C_4$ symmetry, 2D Rashba and 3D Weyl types. These schemes are well accessible with current cold-atom technology, and in particular, a long-lived Bose-Einstein condensation of the 2D Dirac SO coupling has been experimentally proved. The generation of 2D Rashba and 3D Weyl types has an exquisite request that two sources of laser beams have distinct frequencies of factor-two difference. Surprisingly, we find that $^{133}$Cs atoms provide an ideal candidate for the realization. A common and essential feature is the absence of any fine-tuning and phase-locking in the realization, and the resulted SO coupled ultracold atoms have a long lifetime. These schemes essentially improve over the current experimental accessibility and controllability, and open new experimental platforms to study high-dimensional SO physics and novel topological phases with ultracold atoms., Comment: 5 pages, 4 figures, plus supplementary material. Typos are corrected and discussions are updated in supplementary material

Low frequency oscillation is one of the key factors threatening the security and stability of interconnected power grid. Negative damping mechanism low frequency oscillation and forced power oscillation ever have occurred in our country. Based on the center of inertia coordinates, the clustering features of oscillation units are analyzed. The principle for node grouping of low frequency oscillation based on the Pearson correlation coefficient is proposed and the clustering criterion is given. According to the equipment grouping information, the auxiliary control measures calculated by small interference sensitivity can be matched and online determined. In addition, when the local oscillation mode occurs, the method can accurately separate the oscillating source from a plurality of oscillation units. The simulation results of both the 4-machine 2-area system and the Henan electric power system indicate the feasibility and validity of the proposed method.

Non-equilibrium Green’s function method is applied to study the spin thermoelectric effects in a four-quantum-dot ring with two of the quantum dots magnetized. The influence of magnetic configuration on the spin thermoelectric transport through the system is investigated. In some magnetic configurations, a significant spin Seebeck coefficient [Formula: see text] can be generated with the variation of the quantum dot (QD) energy level. Appropriately tuning the QD energy level can let the present device work as a pure spin-up (spin-down) or a pure-spin-current thermal generator. The combined effect of the magnetization and magnetic flux (or Rashba spin-orbit coupling) is also investigated. Finally, the charge figure of merit [Formula: see text] and spin figure of merit [Formula: see text] are evaluated, it is found that the magnitude of the spin figure of merit can be comparable to that of the charge counterpart.