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In this work, mixing and segregation of binary mixtures involving biomass materials in a fluidized bed was experimentally investigated. A frozen bed method was employed to investigate both axial and radial distribution of biomass particles in silica sand. Three different biomass materials were studied: willow sawdust, pelletized soy and oat hull materials. Biomass loading investigated ranged from 5% to 30% by weight. The extent of mixing for each of the biomass composition was investigated using Lacey’s mixing index which is based on the standard deviations of the sample at different axial positions in the bed. The radial composition was also investigated by means of digital imaging analysis using a high-resolution digital camera. The experiments revealed the differences in the extent of particle distribution for pelletized biomass materials vs non-densified materials as a result of differences in particle size, density and importantly, the particle shape of the materials utilized. The results showed an increase in the extent of mixing as the fluidizing velocity increased for both pellet materials while the mixing index for sawdust decreased beyond a loading of 20%. With an increase in biomass loading, an increase in mixing index was found for the two pellet materials. A similar trend was observed for sawdust at the lower loading level. However, the mixing index started to decrease at higher loading level beyond 20%. The results greatly contributed to the understanding of the hydrodynamics of binary and multicomponent mixtures involving biomass materials, especially pelletized materials in fluidized beds.

For the classification of fine-grained images, the subtle differences among the subclasses of the main category must be distinguished. Intuitively, the key to realizing the fine-grained image categorization lies in locating and identifying the detailed differences in the local regions and capturing their feature representations. In this paper, we propose utilizing an attention module combined with a multi-scale latent representation network to locate the discriminative spatial regions, and then learn an accurate attention map to assist the category decision. Furthermore, an attention module is also employed to determine the channel weights of the distinct scale feature maps before the final step. Extensive experiments demonstrate that our model obtains a competitive performance against state-of-the-art baselines on two benchmark datasets, the attention validation experiments further reveal the ability of the model in choosing the proper channel features for low-quality image categorization.

This work proposes a novel Hausdorff fractional NGMC(p,n) grey prediction model based on the NGMC(1,n) model. The new grey model combines the Hausdorff fractional accumulation operator and the Grunwald-Letnikov fractional derivative with more freedom and simpler in calculations; the time response function and recurrence expressions of the new model are deduced by using forward difference; the recurrence relation of the binomial in the discrete solution to avoid calculating the Gamma function and simplifies the calculation; the Grey Wolf Optimizer (GWO) is introduced to optimize parameters of the new model for improving adaptability. To verify the efficiency of the new model, nine existing grey models are used to predict the total renewable energy production, the energy conversion efficiency and the total electricity production of China. The experimental results show that the fitting accuracy and prediction accuracy of the new model are better than those of the other nine existing grey models.

A three-dimensional computational model, coupled with the Large Eddy Simulation (LES) model and Volume of Fluid (VOF) multiphase model, was established to investigate the two-phase flow and slag entrainment during steel bloom continuous casting. The influence of the in-mold electromagnetic stirring (M-EMS), casting speed, and submerged entry nozzle (SEN) immersion depth on the flow pattern and slag entrainment were evaluated. The number, size, velocity, and spatial distribution of slag droplets were counted and the location, velocity and probability of the slag entrainment on the meniscus were exported in real time through a user defined function. The result shows that the slag entrainment mainly occurred around the 1/4 width of the mold. The equivalent diameter of most slag droplets was 2–6 mm under the current casting condition. A formula for the equivalent diameter distribution of slag droplets was proposed according to the statistical result.

In the current study, three-dimensional models were established to simulate the transient formation and dripping of droplets during Electroslag Remelting (ESR) of steel, combining the κ-e two-equation turbulence model, Volume of Fraction (VOF) multiphase model, and Magnetohydrodynamics (MHD) model. The influence of the interfacial tension on the varied size distribution and the transient dripping velocity of droplets were calculated and statistically summarized. The absolute velocity distribution of droplets showed that all the fluid inside the droplet flowed downward, while the relative velocity distribution illustrated a recirculation inside the droplets, indicating that the flow of molten steel inside the droplet have two kinds of motion: a downwards flow due to the gravity and a recirculation inside the droplet which led to the deformation of droplets.With a melting rate of 0.03 kg s−1, the equivalent diameter and the dripping frequency in functions of the interfacial tension were D = 0.0119 σ0.23 and f = 1.45 σ −2.37, respectively.

Laboratory experiments were performed to study the transient evolution of inclusions in Si–Mn-killed stainless steels with additions of 60 and 360 ppm yttrium using low- and high-oxygen yttrium-containing ferroalloys. With the increase of the yttrium content in the steel, the evolution path of inclusions was CaO–Al2O3–SiO2–MnO → Y2O3–Al2O3–SiO2(–CaO–MnO) → Y2O3 and YS → Y2O3. The YS inclusion was generated as a transient product in the steel with 360 ppm yttrium addition using high-oxygen yttrium-containing ferroalloys. With the addition of 60 ppm yttrium, initial larger CaO–Al2O3–SiO2–MnO inclusions were modified to smaller liquid Y2O3–Al2O3–SiO2(–CaO–MnO) inclusions, resulting in a smaller diameter of inclusions. After the addition of 360 ppm yttrium, initial liquid CaO–Al2O3–SiO2–MnO inclusions were modified to small solid Y2O3-rich inclusions, lowering the average diameter of inclusions. Then, the size of inclusions in the steel increased due to the collision of solid inclusions.

Depth estimation is one of the basic and important tasks in 3D vision. Recently, many works have been done in self-supervised depth estimation based on geometric consistency between frames. However, these research works still have difficulties in ill-posed areas, such as occlusion areas and texture-less areas. This work proposed a novel self-supervised monocular depth estimation method based on occlusion mask and edge awareness to overcome these difficulties. The occlusion mask divides the image into two classes, making the training of the network more reasonable. The edge awareness loss function is designed based on the edge obtained by the traditional method, so that the method has strong robustness to various lighting conditions. Furthermore, we evaluated the proposed method on the KITTI datasets. The occlusion mask and edge awareness are both beneficial to find corresponding points in ill-posed areas.

In the current study, the transition of the flow pattern in a 1000 mm × 237 mm continuous casting mold with the injected argon gas was measured using nail boards and the effect of flow pattern on the distribution of non-metallic inclusions along slab thickness was analyzed using an automatic SEM. The flow pattern in the mold transformed from double roll to complex flow and single roll as the argon flow rate increased from 16 to 20 and 30 NL/min. The surface level fluctuation increased with the increasing argon flow rate. The gas flow rate for the mold with the current dimension and a 1.7 m/min casting speed should be less than 16 NL/min to achieve a double roll flow pattern in the mold. Along slab thickness, there were accumulation bands both at the loose side and the fixed side when the flow in the mold was a double roll flow pattern. Only one accumulation band of inclusions near the fixed side was observed when the flow was a single roll in the mold, while inclusions were uniform along the thickness of the slab when the flow was a complex flow in the mold. As the argon flow rate increased from 8 to 20 and 30 NL/min, the number density of 5 μm inclusions gradually decreased along the thickness of the slab. In addition, the area of exposed eyes at the flux layer of the mold and the probability of slag entrainment increased with the increasing of argon flow rate.

Three-dimensional characterization of defects in continuous casting blooms of a heavy rail steel with different electromagnetic stirring intensities at the solidification end, also named final electromagnetic stirring, was performed employing a laboratory-based X-ray computed tomography to evaluate the effect of final electromagnetic stirring on the internal quality of blooms. The three-dimensional distribution and morphology of defects including porosities and oxide inclusions in blooms were characterized. The amount, size and shape complexity of defects increased gradually from the loose-side surface to the center of blooms. The total volume fraction of defects was 5265 and 3942 ppm when the current of final electromagnetic stirring was 200 and 300 A, respectively. The sphericity of defects varied from 0.1 to 0.75, and the equivalent spherical diameter varied between 20 and 450 μm. Most defects with a sphericity > 0.6 were nearly spherical and were assumed to be oxide inclusions. The volume fraction of both porosities and inclusions was small in the chilled layer and the columnar crystal zone and then increased rapidly toward the equiaxed zone. Increasing the current of F-EMS from 200 to 300 A significantly decreased the volume fraction of porosities in the center of the bloom from 2906 to 1873 ppm. It could also decrease the volume fraction and average diameter of oxide inclusions in the bloom by reducing the number of large inclusions.

The effect of electromagnetic stirring at a continuous casting strand on the distribution of inclusions along the thickness of gear steel blooms was investigated. Inclusions in the subsurface of continuous casting blooms were Al2O3·CaO·CaS·MgO, similar to those in the molten steel of continuous casting tundish. Inclusions at 1/4 thickness from the loose side and the center of the bloom were Al2O3·CaS·MgO. The spatial distribution in the number density and composition of inclusions along the thickness from the loose side to the fixed side of the bloom was non-uniform but symmetric. The electromagnetic stirring efficiently improved steel cleanliness by lowering the average number density and area fraction of inclusions in the whole section of the CC bloom from 58.14 #/mm2 and 176.82 ppm to 30.90 #/mm2 and 111.67 ppm, respectively, and by increasing the average size and the maximum size of inclusions from 2.73 and 20.84 μm to 2.99 and 76.02 μm, respectively. More large-size inclusions contained K and Na by the slag entrainment in the mold with electromagnetic stirring were detected than those without electromagnetic stirring. Seven mm of the bloom from the loose side was analyzed for inclusions with size > 1.0 μm every 1 mm depth. The average CaO content of inclusions with size > 1.0 μm within the 7 mm subsurface of the bloom increased from 5.67 wt pct without electromagnetic stirring to 16.12 wt pct with electromagnetic stirring and increased from 10.24 wt pct without electromagnetic stirring to 21.31 wt pct with electromagnetic stirring for > 3.0 μm inclusions, which confirmed that unreasonable current electromagnetic stirring operation parameters will lead to slag entrainment.

Scaled-down models have been extensively employed to study fluid flow phenomena in metallurgical ladles. The geometric scale factor in the models employed varies by one order of magnitude. A minimum value for the geometric scale factor for metallurgical ladles has not been reported before. In this study, mixing time in four different geometric scale ladles with one nozzle was measured as a function of gas flow rate, nozzle radial position, and oil thickness, using the electric conductivity method. Dynamic similarity was discussed in detail. Mixing time predicted and measured, according with dynamic similarity principles, was evaluated for the four ladles. The main finding from this work is that in principle dynamic, similarity can be achieved in all four ladles with different geometric scale ratios; however, it is evident that the experimental conditions can impose a limit to the geometric scale ratio.

Coke–slag–metal samples located near the deadman edge and below the taphole of blast furnace were obtained by core drilling after cooling. The chemical composition, microstructure, phase composition and distribution of samples were studied in detail. In addition, the graphitisation degree of coke in hearth was also investigated. The results showed that coke larger than 60 mm still existed (more than 1%). Pores in coke are filled with molten slag and a small part of liquid iron. The pores in hearth coke are not completely filled, but there is still plenty of micropore, with a volume of less than 1 mm. There are also a little alkali metals (K and Na) in ash, which causes the deterioration of coke. The iron–carbon interface is covered by a slag layer. The coke remained in deadman long enough to undergo the graphitisation process.

Transition-metal sulfides (TMSs) were demonstrated to be heartening anodes for sodium-ion batteries (SIBs) because of their alterable nanostructures, large theoretical capacity and environmental friendliness. Whereas, the relatively poor rate and cycling capability of TMSs still hinder the rapid development of their practical applications. Herein, a novel CuS nanocable self-assembled by hierarchical nanosheet is designed as SIB anodes, which delivers a large capacity (367 mAh g−1 at 5 A g−1), excellent rate capacity and cycle performance (213 mAh g−1 after 2000 cycles at 15 A g−1). The uniquely hierarchical nanostructure can both contribute more effective and durable active sites and shorter diffusion length of sodium ions/electrons. Besides, ex situ XRD, HRTEM and SAED reveal the phase transformation during sodiation process and the reaction mechanism of as-synthesized CuS nanocables. These results can offer new clues and inspirations to understand the relationship between the designed nanostructures and sodium storage behaviors of other TMSs.

The visualization of the thawing and desaturation process on an initially saturated, frozen gas diffusion layer (GDL) with a serpentine gas flow channel was performed based on synchrotron X-ray computed tomography images. High speed CT scanning during the experiments allowed the dynamic desaturation process to be quantified under the cold-start with air purging condition. The saturation profiles and the desaturation rates were studied over the entire GDL domain, through-plane, and in selected regions of interest for localized behavior. Sigracet 35AA and 35BA GDLs were selected for the experiments to study the effects of GDL hydrophobicity. Along with the real-time saturation profiles, the average desaturation rates for the entire GDL domain over the whole purging process were 0.000186 μL cm−2 s−1, 0.000470 μL cm−2 s−1, 0.000516 μL cm−2 s−1 and 0.000901 μL cm−2 s−1 with the superficial gas velocity of the purging air at 2.88 m/s, 4.26 m/s, 5.98 m/s and 9.02 m/s, respectively. In addition, the dynamic saturation contours and 3-D GDL geometry models were constructed to show the liquid water movement through a GDL. Although the GDL desaturation curves for each experiment share similar trends, the results show that different conditions including air flow rate, GDL geometric location, initial water saturation, and GDL boundary condition could cause heterogeneous desaturation behavior on both overall and localized GDL regions. These data provide valuable information for future modeling studies that involve the thawing process in the GDL, and could be used to optimize the cell design and develop cold-start protocols.

A mathematical model coupled with the penetration theory, the ion and molecule coexistence theory, and thermodynamic equilibrium was proposed for predicting the composition evolution of inclusions in the molten steel during the electroslag remelting process. The model was used to evaluate the transformation of composition of inclusions in a plain carbon steel and the mechanism of the transformation of inclusions was accurately revealed, which was mainly the mass transfer of aluminum through steel/slag reactions. The rate of the transformation of inclusions composition was the lowest in the metal pool, while that in the slag pool was the fastest which was due to the acceleration of reactions by higher temperature and faster fluid flow. Inclusions with smaller diameter had faster transformation rate, but had less content of Al2O3 in the final composition. The size of droplet showed little influence on the transformation of composition of inclusions. When the content of Al2O3 in the slag increased from 20 to 50 wt pct, the calculated content of Al2O3 in the final inclusions increased from 79 to 90 wt pct, approximately. The low content of Al2O3 in the slag was beneficial to the removal of aluminum in the steel, while the high content of Al2O3 in the slag increased the content of total aluminum in the steel.

Alloys strengthened by nanometer-sized Laves phases have been used as structural components working in corrosive environments at high temperatures owing to the favorable physical and chemical properties of Laves phases. However, due to the small sizes of Laves phases in alloys, their precise characterization cannot be realized efficiently by the existing methods. We previously found that under irradiation of a polished Zircaloy-4 alloy [Zr–1.50Sn–0.25Fe–0.15Cr (wt.%)] with a focused, low-energy (30 keV) electron beam, surface Zr atoms in the α-phase matrix, instead of the ones in nanometer-sized Zr(Fe, Cr)2 Laves phases, were able to undergo significant sputtering into vacuum in a field-emission scanning electron microscope (FE-SEM), resulting in the exposure of the Laves-phase nanoparticles (NPs). Based on this surprising physical phenomenon, here we successfully develop a methodology for performing statistical characterization of Laves-phase NPs in fully recrystallized Zircaloy-4 alloys as well as their partially recrystallized counterparts. By comparing the attributes of the Laves-phase NPs in both partially and fully recrystallized alloys, the conventional, tiny Ostwald ripening of the Laves phases was, for the first time, found to occur during the alloy recrystallization process. These understandings are likely to elucidate the universal mechanisms underlying the nucleation and growth of Laves-phase NPs in solid solutions.

A biosorbent derived from oat hulls was employed to dehydrate butanol from water mixture to obtain a high-purity butanol product. As this process involves water and butanol binary sorption, it is i...

The bonding behaviors of the plate-concrete interface of a composite structure consisting of a concrete block in the middle and two cement plates at both sides play a key role in its overall mechanical performance. In this paper, the authors conduct 3 groups of push-out shear tests on a total of 39 composite samples to assess the bonding performance. The influence of the FRP cement plates, the concrete strength, and the ribs installed in the cement plate on the interfacial shear strength, the relative bond-slip, strain, and the failure modes of the composite samples is recorded and analyzed. The results show that (1) the shear strength and bond-slip performance of the interface are largely improved if the GFRP/BRRP cement plates are used; (2) shear strength of the interface increases with the concrete strength, while the deformation behaviors show no significant improvement; (3) an inclusion of the ribs to the interface enhances the shear strength and shear stiffness but decreases the maximum relative slip at failure; (4) most of the samples present the shear failures along the interface; however, the bending shear failure prior to the interface shear failure is also observed on the concrete block for low concrete strength samples and the samples with ribs; and (5) regression method is used to develop a constitutive model of the stress-slip at the interface to describe the relationship between the shear strength with the cement plates, the concrete strength, and ribs.

The mathematical model of coupling fluid flow, heat transfer, solidification, solute transport, and the electromagnetic field of the bloom in the upper part of the strand was established with three nozzle types. Then, the flow field, distribution of the temperature, solidification, and macrosegregation of carbon were investigated and compared by numerical modeling. In the case of the straight submerged entry nozzle (SEN), the molten steel flows down deep into the liquid pool, and the depth of the jet flow reaches about 1.0 m beneath the meniscus. The jetting zone is the high-temperature zone. In the case of two-port SEN and four-port SEN, the flow patterns and distribution of temperature in the central longitudinal section are similar. The jet flow impinges directly on the initially solidified shell and then it is divided into two longitudinal circulations. The heat of molten steel is dissipated along with the longitudinal circulations. The negative segregation band was generated near the bloom surface due to the washing effect by the rotating flow at the solidification front with three nozzle types. The negative segregation deteriorates gradually with the number of ports decreasing.

Plain strain deformation trials were carried out on samples of pipeline steels at 1473 K, 1673 K and 1723 K, respectively. The deformation of inclusions in the solid steel at different temperatures and in the semi-solid steel was studied. The composition of inclusions changed from 60.62%Al2O3–16.10%CaO–10.27%MgO–13.01%CaS before deformation to 60.59%Al2O3–13.03%CaO–12.74%MgO–13.63%CaS, 59.69%Al2O3–7.04%CaO–11.51%MgO–21.76%CaS, and 68.26%Al2O3–22.56%CaO–6.68%MgO–2.5%CaS with corresponding deforming temperatures of 1473 K, 1673 K and 1723 K. While the average aspect ratio of inclusions increased from 1.28 to 2.23, 1.32, and 1.35, respectively. Thermodynamic calculations performed by FactSage 7.0 verified the composition transformation from CaO to CaS during the solidification and cooling process of the steel. A kinetic model was used to calculate the dynamic transformation of the inclusion composition at compression temperatures. The inclusion transformation ratio from CaO to CaS increased from 38.28% at 1473 K to 50.50% at 1673 K. For the deformation in the solid steel at the temperature below 1673 K, the thickness of the hard phase CaS increased with the soaking temperature, while the hardness of the steel matrix decreased. The larger hardness difference between inclusions and the steel matrix led to a higher aspect ratio of inclusions after deformation. For the deformation in the semi-solid steel, the small difference of hardness between the soft inclusion phase and the soft steel matrix resulted in a low aspect ratio of inclusions in the semi-solid steel after deformation.

A three-dimensional computational model, combining the large eddy simulation (LES) turbulent model, VOF multiphase model for air phase, and discrete phase model (DPM) for injected bubbles, was established to evaluate the effects of drag force, lift force, pressure gradient force, virtual mass force, and wall lubrication force on the fluid flow and spatial distribution of bubbles in a continuous casting (CC) strand. The effect of lift force and wall lubrication force on the fluid flow was achieved via a user defined subroutine (UDF). The contribution of interphase forces was quantitatively evaluated using UDF. The appropriate interphase force model was determined by comparing the predicted fluid flow and bubble distribution in the CC strand with the measured results one using particle image velocimetry (PIV). The interphase force had a significant effect on the spatial distribution of bubbles and the flow field near the meniscus. The drag force and buoyancy force were the dominant ones at low turbulent kinetic locations. Moreover, the magnitude of the lift force, pressure gradient force, and virtual mass force was increased sharply at high turbulent kinetic locations, approximately one to two orders greater than that of the buoyancy force.

To enhance the removal of B from metallurgical-grade Si (MG-Si) by the CaO-SiO2-CaCl2 slag refining technique, Ar gas was injected during the refining process. The effects of the refining time, Ar gas flow rate, and the blowing-pipe immersion depth on the removal of B from MG-Si were studied. The results show that the injection of Ar gas can effectively stir and then mix the Si and slag phases, resulting in an increase in the Si/slag contact area and in an acceleration of the mass transfer rate of B. With the combined slag-refining and Ar gas-blowing approach, the reaction time for the removal of B was reduced to 5 min from 75 min required with the slag-refining approach. Correspondingly, the content of B was reduced from 23.91 to 10.42 ppmw, with a removal efficiency of 56.42%. The results were confirmed by the coupled large-eddy simulation model and the volume of fluid multiphase flow model.

Titanium-based materials have been considered to be promising materials for many years. The structures and properties of TixOy and TiC at the nanoscale are important for studying the mechanism of formation of their nanoparticles. In this work, the density functional theory (DFT) method was used to calculate the structures of (TixOy)n (n = 1-5) and (TiC)n (n = 1-10) clusters. Based on these calculations, the formation pathways from (TiO2)n clusters to (TiO)n and (TiC)n clusters via carbon reduction were investigated. The results show that the pathway via (Ti2O3)n or (Ti3O5)n is the most likely pathway for the transformation of the (TiO2)n cluster to the (TiO)n cluster. The (TiO)n cluster is not the final product in the reduction process of (TiO2)n with C, and it can be finally transformed into (TiC)n clusters via various TinOxCy clusters via reaction with C. In addition, the (TiO2)n clusters can be transformed into (TiC)n clusters directly via various TixOyCz clusters.

Observing and measuring wet granulation processes of pharmaceutical powders is challenging with conventional experimental methods due to their opacity and the complex interaction that happens in a short time. In this study, synchrotron in-situ imaging technique was employed to capture the dynamic granulation process with a single drop impacting method. Two common pharmaceutical excipients and an active pharmaceutical ingredient (API) were used as the powder beds. Three liquids were used as binders. A new parameter, overall movement ratio, rm, is introduced to quantitatively describe the movement of the liquid binders in the powder beds. The dynamic interactions between the liquid binder and solid powders were captured via high temporal and spatial resolution X-ray images. Results show that particles with smaller sizes have the tunneling mechanism, and the spreading mechanism occurs with larger particles, as expected. Liquid binder properties including viscosity and contact angle, and operation parameters including droplet release height and volume show significant impacts on the dynamic granulation process. This study demonstrates the potential of using in-situ synchrotron X-ray imaging to quantitatively study the dynamic wet granulation process.

In the current study, the transformation in the composition of non-metallic inclusions from the molten steel to the solidified steel was studied and the composition distribution of inclusions on the cross section of a linepine continuous casting slab was predicted. During cooling and solidification of the continuous casting strand, Al2O3-CaO inclusions reacted with the bulk steel and transformed to CaS-Al2O3-MgO-(CaO) ones in the continuous casting slab. The composition of inclusions on the cross section of the slab varied with locations due to the varied cooling rate. A model was established to predict the distribution of the composition of inclusions on the cross section of the continuous casting slab, coupling solidification and heat transfer of the continuous casting slab, the kinetic mass transfer of the dissolved elements in the solid steel, and thermodynamic calculation of inclusion transformation at different temperatures. The composition transformation of inclusions mainly occurred at the temperature between the liquidus and solidus of the linepipe steel. Inclusions were mainly CaS-Al2O3-MgO-(CaO) in slab center and were MgO-Al2O3-CaO-CaS within the subsurface of the slab. In the slab, the transformation fraction of inclusions was less than 10 % at corners while it reached 70 % at 50 mm below the surface of the slab.

The initial growth mode of oxide on alloy plays a decisive role in the development of protective oxide scales on metals and alloys, which is critical for their functionality for high temperature applications. However, the atomistic mechanisms dictating that the oxide growth remain elusive due to the lack of direct in situ observation of the initial oxide nucleation and growth at atomic-scale. Herein, we employed environmental transmission electron microscopy and the first-principles calculations to elucidate the initial atomic process of nickel-chromium (Ni-Cr) alloy oxidation. We directly revealed three different oxide growth modes of initial NiO islands on Ni-Cr alloy upon oxidation by O2, which result in distinct crystallography and morphology. The multimode oxide growth leads to irregular-shaped oxides, which is shown to be sensitive to the local mass transport. This localization of oxide growth mode is also demonstrated by the identified vigorous competence in oxide growth and thus shown to be kinetically controlled. The concept exemplified here provides insights into the oxide formation and has significant implications in other material and chemical processes involving oxygen gas, such as corrosion, heterogeneous catalysis, and ionic conduction.

Surface compositional and phase segregation in an alloy can change its functionality, especially for applications where surface structure and chemistry play a vital role. For instance, the surface status of alloy catalysts significantly affects their catalytic performance for both heterogeneous and electrochemical processes. Surface segregation is believed to be driven by the difference in surface energy to reduce the total free energy of the alloy. However, the atomistic processes during the segregation process remain elusive, especially for gas molecule-induced segregation, where both structural and chemical reordering may occur. Herein, we achieved in-situ atomic-scale visualization of the surface segregation behaviors of a solid solution Cu(Au) alloy under the CO gas by an aberration-corrected environmental transmission electron microscope. CO-induced Cu(Au) surface ordering structures largely change the surface chemistry of the alloy. Further gas exposure at elevated temperature could facilitate Au atom diffusion through a specific “atomic channel” structure for dealloying and clustering on the surface. The segregated Au nanoparticles show rich phase and morphological dynamics interacting with the alloy surface, where the gas adsorption also plays an important role. These atomic insights provide direct evidence for the surface segregation and dealloying mechanisms of bimetallic alloys, and highlight the role of gas adsorbate in these surface processes.

Three-dimensional numerical simulations of rotating detonation engines (RDEs) are reported with stoichiometric hydrogen/air mixtures using Navier-Stokes equations with non-slip walls. The effects o...

Unique self-assembled iron(II) molybdenum (IV) oxide (Fe2Mo3O8) mesoporous hollow spheres have been facilely constructed via the bubble-template-assisted hydrothermal synthesis method combined with simple calcination. The compact assembly of small nanoparticles on the surface of the hollow spheres not only provides more active sites for the Fe2Mo3O8, but also benefits the stability of the hollow structure, and thus improved the lithium storage properties of Fe2Mo3O8. The Fe2Mo3O8 mesoporous hollow spheres exhibit high initial discharge and charge capacities of 1189 and 997 mA·h·g−1 respectively, as well as good long-term cycling stability (866 mA · h · g−1 over 70 cycles) when used as a lithium-ion battery anode. This feasible material synthesis strategy will inspire the variation of structural design in other ternary metal molybdates.

Experiments were carried out to investigate the deformation and fracture of non-metallic inclusions in steel at different temperatures. The deformation of inclusions at high temperature could be characterized by viscosity. Meanwhile, the apparent deformation of inclusions at high temperature was also related to the difference of viscosity between inclusions and the steel matrix. Lower inclusion viscosity leads to better deformability when the viscosity of inclusions was smaller than that of steel matrix, otherwise, the inclusion deformation would be limited. The Young's modulus of inclusions could be used to characterize the deformation of inclusions at low temperature. Generally, the deformation of inclusions at low temperature increased with the decrease of Young's modulus. The intrinsic reason for the different characterization parameters of inclusion deformation at different temperatures was supposed to be the brittle to ductile transition phenomenon of inclusions in the process of temperature change. The work provided new ways to control the deformation of inclusions, for instance, by adjusting the temperature and strain rate during the processing of steel.

Silicon growth from Si–Fe melts was investigated in view of producing high-quality Si using induced temperature gradients. Scanning electron microscopy coupled with energy-dispersive spectroscopy and micro-computed tomography analyses were used to characterize the quality of bulk Si, in particular its microstructure and purity. The migration of Si and Fe atoms along a temperature gradient in the mushy zone of the Si–Fe alloy was evidenced, which became the source of Si precipitation on the C substrate, and ultimately forming bulk Si. Furthermore, the content of residual Fe–Si can be decreased in the bulk Si by controlling the temperature gradient, the holding time, and the alloy composition.

Surface deformation has become an important factor affecting urban development. Lanzhou is an important location in the Belt and Road Initiative, an international development policy implemented by the Chinese government. Because of rapid urbanization in Lanzhou, surface deformation occurs easily. However, the spatial-temporal characteristics of surface deformation and the interaction of driving forces behind surface deformation in Lanzhou are unclear. This paper uses small baseline subset InSAR (SBAS-InSAR) technology to obtain the spatial-temporal characteristics of surface deformation in Lanzhou based on 32 Sentinel-1A data from March 2015 to January 2017. We further employ a geographical detector (geo-detector) to analyze the driving forces (single-factor effects and multifactor interactions) of surface deformation. The results show that the central urban area of Lanzhou was stable, while there was surface deformation around Nanhuan road, Dongfanghong Square, Jiuzhou, Country Garden, Dachaiping, Yujiaping, Lanzhou North Freight Yard, and Liuquan Town. The maximum deformation rate was −26.50 mm year−1, and the maximum rate of increase was 9.80 mm year−1. The influence factors of surface deformation in Lanzhou was a complex superposition relationship among various influencing factors, not a result of the single factor. The interaction between the built-up area and land cover types was the most important factor behind surface deformation in Lanzhou. This paper provides the reference data and scientific foundation for disaster prevention in Lanzhou.

Products of Al-deoxidation reaction in iron melt are the most common inclusions and play an important effect on steel performance. Understanding the thermodynamics on nano-alumina (or nano-hercynite) is very critical to explore the relationship between Al-deoxidation reaction and products growth in iron melt. In present study, a thermodynamic modeling of nano-alumina inclusions in Fe–O–Al melt has been developed. The thermodynamic results show that the Gibbs free energy changes for the formation of nano-Al2O3 and nano-FeAl2O4 decrease with the increasing size and increase with the increasing temperature. The Gibbs free energy changes for transformation of nano-Al2O3 into bulk-Al2O3 increase with the increasing size and temperature. The thermodynamic curve of nano-alumina (or nano-hercynite) and the equilibrium curve of bulk-alumina (or bulk-hercynite) obtained in this work are agree with the published experimental data of Al-deoxidation equilibria in liquid iron. In addition, the thermodynamic coexisting points about Al2O3 and FeAl2O4 in liquid iron are in a straight line and coincide with the various previous data. It suggested that these scattered experimental data maybe in the different thermodynamic state of Al-deoxidized liquid iron and the reaction products for most of the previous Al-deoxidation experiments are nano-alumina (or nano-hercynite).

Axial ultrasonic vibration–assisted cutting has been proposed and proved preponderance on cutting performance; however, the transient separation cutting characteristic has not been clearly revealed. This paper focuses on the transient separation cutting characteristic of axial ultrasonic vibration–assisted cutting and its influence on the cutting performance. First, the separation cutting criteria, including feed coefficient and phase shift, are established and influence factors, such as feed rate, amplitude, and phase shift, are systematically analyzed. Subsequently, the duty ratio is deduced and calculated, and some features and a control mechanism are introduced. In addition, a transient separation cutting model with four stages is demonstrated. The reason for the average cutting force reduction by the transient separation cutting characteristic is also stated. Finally, the verification of the separation cutting and transient separation cutting model and the comparison of the feed thrust force and parameter influences on the cutting performance are experimentally performed. The transient signals of different duty ratios 0.55 to 1 are obtained, and 10 to 40% reductions of feed thrust are measured both by a PCB sensor and a Kistler dynamometer. The influence degree of the feed coefficient, spindle rotation speed, and cutting depth on the performance is analyzed. A parameter combination of smaller feed coefficient, moderate spindle rotation speed, and smaller cutting depth is suggested to obtain a better cutting performance by fully considering the cutting force, surface roughness, and tool life.

In the current study, two plant trials for the ladle refining process without and with the calcium treatment were compared to investigate the effect of the calcium treatment on the inclusion deformation in Si-Mn-killed 18Cr-8Ni stainless steels. The total aluminum rose from 10 ppm to 25 ppm due to the slag and steel reaction, increasing the Al2O3 in inclusions during the ladle refining process. Without the calcium treatment, inclusions changed from Al2O3-SiO2-MnO-CaO with about 20% MnO to Al2O3-MgO-SiO2-CaO with about 10% MnO. The calcium treatment obviously lowered Al2O3 and MnO in inclusions and led to the formation of CaO-rich inclusions. Inclusions changed from Al2O3-SiO2-CaO-MnO to SiO2-CaO-Al2O3 after the calcium treatment of Si-Mn-killed stainless steels. Calculations showed that the calcium treatment of 15−25 ppm lowered the melting temperature of inclusions but further additions increased the melting temperature. Calculations also showed that calcium addition lowered Young’s modulus. Calcium treatment was an effective method to improve the deformability of inclusions in Si-Mn-killed stainless steel during the cold rolling process.

Microstructural evolution during severe plastic deformation and mixing of Mg95.8Zn3.6Gd0.6 and Mg97Cu1Y2 (at%) alloys upon friction stir welding was studied. A laminated onion-ring structure composed of alternative distribution of layers with significantly refined microstructures from different alloys was formed in the stirred zone. Coarse quasicrystals were broken up and dispersed with most of them being transformed into cubic W-phase particles, and thick 18R long-period stacking ordered plates were fractured and transformed into fine 14H-LPSO lamellae in the stirred zone (SZ) experiencing complex material flow under high strain rate. Fine W-phase particles and 14H-LPSO lamellae formed during dissimilar friction stir welding (FSW) usually have no specific orientation relationship with surrounding Mg matrix. Chemical measurements demonstrated occurrence of interdiffusion between dissimilar layers in the SZ. Phase transformation was observed for some particles of quasicrystals and long-period stacking ordered (LPSO) in regions slightly outside the SZ. An ultimate tensile strength of ~ 415 MPa and an elongation to failure of ~ 27.8%, both exceeding those of base materials, were obtained in the SZ, due to microstructural refinement and formation of a laminated structure.

We introduced a parameter rs (the radius of the pores where the meniscus forms), which is composed of two factors, i e, water loss and cumulative pore size distribution (PSD), to provide a better explanation of the influence of superplasticizers(SPs) on early-age drying shrinkage. In our experiments, it is found that the addition of three types of SPs leads to a significant increase in the early-age drying shrinkage of cement paste, and drying shrinkage increases with the dosage of SPs. Based on the results above, we further studied the mechanism of the effects of SPs on the early-age drying shrinkage of cement paste by PSD and water loss, which are two components of rs. The experimental results indicate that rs can be a better index for the early-age drying shrinkage of cement-based materials with SPs than a single factor. In addition, the effects of SPs on other factors such as hydration degree and elastic modulus were also investigated and discussed.

Raindrop size distribution (DSD) characteristics during the East Asian summer monsoon (EASM) were studied, using measurements from three OTT Particle Size Velocity (Parsivel) disdrometers in Nanjing, Chuzhou, and the northwestern Pacific (NWP), respectively. Western and eastern parts of the monsoon rainband were separated for a comparative study of the DSD variability. Along with disdrometer data, GPM Dual-Frequency Precipitation Radar (DPR), Fengyun-2E (FY-2E), MODIS, GPCP, ERA-Interim, and in situ radiosonde datasets are combined to illustrate the possible microphysical mechanisms for the significant DSD variability in two parts, in terms of convective intensity, cloud structure, and aerosol effects. The DSD characteristics of six rain-rate classes and two rainfall categories (convective and stratiform) were studied. The western part has larger mass-weighted mean diameter Dm while smaller normalized intercept log10(Nw) than the eastern part, and the convective clusters of the western part (land) could be identified more maritime-like than continental-like due to moisture transport from the tropical ocean, while that of the eastern part (sea) is between maritime-like and continental-like. Cross validation of GPM rainfall products are implemented based on surface disdrometer observations. DPR products manifest better performance over sea than land areas of the EASM rainband. Empirical Dm–Ze and Nw–Dm relations were also derived preliminarily to improve the GPM rain-retrieval algorithms in the EASM season.

Laboratory experiments were conducted to study the transformation of cerium-containing inclusions during the solidification and cooling process in ultra-low-carbon aluminum-killed steels with 33 ppm, 83 ppm and 140 ppm. Inclusions were analyzed statistically using an automatic scanning electron microscope in water-cooled and furnace-cooled samples, respectively. Besides, sulfur-containing precipitates were detected in furnace-cooled ingots to validate the transformation of inclusions. During the solidification and cooling process, it was found that homogeneous CeAlO3 inclusions transformed into Al2O3–Ce2S3 dual-phase ones in the steel containing 33 ppm, and Ce2O2S inclusions transformed into CeAlO3–Ce2S3 or Al2O3–Ce2S3 dual-phase ones in the steel containing 83 ppm, while inclusions in the steel containing 140 ppm hardly transformed. The thermodynamic analysis was performed and agreed well with experimental results. A prediction model based on the thermodynamics and the mass balance was established to predict the type and the composition of inclusions after transformation in ingots. When the value of T.Ce/T.S ≥ 2.92 in the steel, all sulfur content was combined with the cerium and precipitates of (Mn, Cu)S hardly formed in the solidified steel.

Zeroth-order spatial electromagnetic force wave has been regarded as one of the main sources for electromagnetic vibration and noise of integer slot multipole permanent magnet synchronous machine (PMSM) used in electric vehicles. In this study, the 48-slot-8-pole built-in permanent magnet synchronous motor for a vehicle was taken as an example. The main sources and characteristic parameters (frequency and amplitude) of the zeroth-order force wave of the integer slot multipole PMSM were presented. Based on this, a method of stator and rotor structure optimisation was proposed to effectively reduce magnitudes of vibration and noise for the machine by increasing the natural frequency and reducing the harmonic content and amplitude of electromagnetic force waves. The comparison of the noise reduced machine with the initial design was experimentally validated.

Industrial trials and thermodynamic analysis were performed to investigate the transient influence of cerium on inclusions in an Al-killed non-oriented electrical steel. Inclusions were statistical...

In the current study, the wettability between 304 stainless steels and refractory materials was investigated using the sessile drop method in a reducing atmosphere at 1550 °C. The contact angle between the stainless steel and the original refractory was 133°, and was 126° between the stainless steel and the used refractory. The lower dissolved oxygen content in the stainless steel after the reaction with the original refractory was responsible for the higher contact angle. Adhesion work of original and used refractories per mole was 41 kJ/m and 53 kJ/mol, respectively, indicating that the physical bond energy was dominant at the interface between the stainless steel and the refractory. The penetration of the steel into the used refractory was more serious than that into the original refractory, which was mainly influenced by the angle between the liquid drop meniscus and refractory pores based on the force analysis. The liquid slag phase formed in the refractory at the high temperature entered refractory pores, decreased the meniscus angle and promoted the steel penetration.

The present work depicts advanced understanding of dynamic behavior of droplets in serpentine channels for proton exchange membrane (PEM) fuel cells using a synchrotron-based X-ray radiographic technique at the Canadian Light Source (CLS). Due to high photon flux, the synchrotron-imaging technique provides high temporal and spatial resolution of images of water droplets in gas flow channels for PEMFCs. The whole cell and in particular, the gas diffusion layer (GDL) were operated under elevated temperatures through a self-designed heating channel around the GDL area (25–75 °C). In the experiments, a Sigracet 35 BC GDL was employed, and droplet height, chord and cycle time were measured over a series of images collected. Experimental results show that the droplet cycle time had been significantly reduced to less than 0.5 s from 14 s with an increase in the operating temperature from 25 °C to 75 °C. In addition, it is also found that increasing the operating temperature decreases the critical dimension of water droplets upon detachment i.e. from 0.46 mm for 25 °C to 0.33 mm for 75 °C. at a superficial gas velocity of 5.98 m/s.

Industrial trials were performed to investigate the evolution of inclusions in the molten steel of the continuous casing tundish and the bloom of a heavy rail steel, and the spatial distribution of inclusion composition along the bloom thickness was studied. An integrated model was established to predict the spatial distribution of the inclusion composition on the entire cross-section of a heavy rail steel continuous casting, which coupled the heat transfer and solidification of steel during continuous casting, the thermodynamic transformation of inclusions with temperature and the kinetic diffusion of dissolved elements in the steel. Both industrial trials and model predictions achieved similar conclusions.Inclusions within the 30 mm subsurface layer had a similar composition and size to those of the molten steel and were more than other locations of the bloom and at 1/4 thickness of the bloom inclusions were larger and contained the biggest concentration of CaS. Along the thickness of the bloom, an opposite fluctuation of CaO to that of CaS in inclusions existed so that the main reaction between the inclusion and the steel matrix was (CaO) + [S] = (CaS) + [O]. When the cooling rate was larger than 150 K/s, the newly precipitated CaO–Al2O3–MgO–SiO2–(10 pct CaS) ones. In order to achieve an optimized composition of inclusions, the total oxygen and aluminum in the steel should be

Plastic deformation and fracture behavior of Cu/V nanoscale metallic multilayers (NMMs) were systematically investigated through in situ transmission electron microscopy testing. Two different types of interfaces: sharp interfaces and interfacial transition zones (ITZs), formed in the as-fabricated Cu/V NMMs. Upon deformation, sharp interfaces and ITZs exert distinct influences on the fracture behavior of Cu/V NMMs. Sharp interfaces can impede the crack propagation by deflecting the crack propagation and blunting the crack tip, while the ITZs can induce microcracks and facilitate the fracture process. These findings shed light on the important roles of interface structures in the deformation of a broad class of NMMs.

The unburned carbon in fly ash is an important indicator of the coal-fired boiler combustion efficiency. Laser-induced breakdown spectroscopy (LIBS) has been applied for measurement of unburned car...

Training models to approximate target systems is the dominant method applied to unknown-structure delay system modeling. Due to limited learning ability of the models, the time-delay estimation (TDE) process should be executed prior to the training. The TDE for unknown-structure multi-input multi-output (MIMO) delay systems remains a challenge due to the physical interaction within the system the correlations among the system inputs and outputs. This paper addresses the TDE problem of unknown-structure MIMO delay systems. A dependence measure employed from copula theory, which is named C-dependence, is introduced to measure the dependence among the system inputs and outputs. The relationship between the C-dependence and the time-delays is studied, and the time-delays are estimated by maximizing the C-dependence. The highlight of the proposed method is that no prior decoupling process and system structure are required during the TDE process. Simulation and real data experiments are provided to demonstrate the effectiveness of the proposed method.

The effect of cerium on inclusions in an ultra-low-carbon Al-killed steel was studied at 1873 K (1600 °C) using laboratory experiments. The content of cerium in the steel varied from 0 to 0.028 wt pct. The contents of the total oxygen (T.O), total nitrogen (T.N), total sulfur (T.S), total cerium (T.Ce) and dissolved aluminum ([Al]) in the steel samples 1, 5, 10 and 30 minutes after adding cerium were measured, and inclusions were characterized using an automatic scanning electron microscope. It was found that a cerium-concentrated zone formed after the cerium alloy was added to the molten steel. Many inclusions were generated in the cerium-concentrated zone and then disappeared with the decrease of the cerium content. The variation of the inclusion composition was Al2O3 → CeAlO3 → Ce2O2S → Ce2O2S + CeS with the increasing cerium content in the steel, which agreed well with the thermodynamic analysis. The value of T.Ce/T.O was able to evaluate and predict the type of inclusions. A prediction model of the composition of inclusions was established based on thermodynamic calculation and mass balance and was validated by experimental data. When the value of T.Ce/(T.S + T.O) was ≥ 4.4, the average composition of inclusions changed little since most inclusions were fully modified.

Industrial experiments and thermodynamic calculations were performed to investigate the evolution of non-metallic inclusions during cooling and solidification of GCr15 bearing steels with different...