It is very important to understand the influence of impurity elements on the quality of boron carbide and control impurity elements. In the present work, boron carbide powders with different impurity levels were sintered by hot pressing under the same conditions, in which a set of aggregation pores and secondary phases can be detected. The reaction and distribution of impurities in the sintering process were analyzed. The mechanism of impurities on densification and pore generation is discussed. It can be found that the Fe₂O₃ and SiO₂ will react with boron carbide to form FeB, FeB₄ and Si₅C₃, and the impurities cause significant aggregation pores and promote the abnormal grain growth, which have an unapparent influence on hardness and strength but sharply decline the toughness of sintered B₄C samples from (1.97±0.03) MPa·m^1/2 to (0.33±0.04) MPa·m^1/2.

To investigate the flow behavior of Mg-10Gd-3Y-0.4Zr magnesium alloy during high-temperature deformation, the thermal compression experiments were conducted in the temperature range of 573–773 K and strain rate range of 0.001–1.0 s⁻¹. The experimental results showed that the flow stress decreases with the increase in temperature and decrease in strain rate. The variation of rheological stress was related to the strain change and the improved Arrhenius constitutive equation considering the strain compensation was established. However, the Arrhenius model with strain compensation showed obvious deviation in the true stress–strain curves at low temperature and high strain rate. The error analysis shows that the material parameters in Arrhenius model were not only related to strain, but also to strain rate and deformation temperature. Therefore, a modified Arrhenius-type constitutive model was established by considering the relationship between the material parameters and the forming parameters in high-temperature compression by comparing the calculated stress in the modified model with the experimental stress, the modified Arrhenius model established in this study can accurately predict the rheological stress of Mg-10Gd-3Y-0.4Zr magnesium alloy in all conditions during the high-temperature compression.

Effect of strain path change on mechanical properties, formability, and forming limit of 1050 aluminum alloy is discussed experimentally in this study. Various strain paths are done in three modes of unidirectional, reverse, and cross rolling. Grain size, hardness, stress–strain diagram, and forming limit in two ratios of 20% and 40% for three rolling modes are compared. Results show that the grain size in rolled sheet in cross mode is smaller than that in other modes. Moreover, the strength and elongation of unidirectional and cross rolled samples sheets are more than those of other modes. In contrast, the hardness of the rolled samples in unidirectional and cross modes is almost equal and more than that of reversed samples. Moreover, cross rolling of sheet leads to normal anisotropy decrease, in which that

craves to 1. Forming limit of rolled sheets is developed significantly in cross mode compared to other modes, in a way that for 40% reduction ratio, the amount of FLC₀ is 0.113 for cross rolling, 0.09 for unidirectional rolling and 0.081 for reverse rolling. Forming limit in unidirectional and reverse rolling modes is a function of the loading path.

Capacitive deionization (CDI) is a promising technology for removing salt from brackish water, and the desalination performance greatly depends on the structures and properties of electrode materials. In this work, the ZIF-67 was used as a precursor to obtain three ZIF-67-derived porous carbon nanomaterials including carbon nano-box (ZCNB), carbon nanotubes (ZCNT), and carbon nano-box and carbon nanotube hybrids (ZCNH). The pore structures, surface properties, electrochemical properties, CDI performances of three porous carbon nanomaterials and constitutive relationships were investigated. The results show that among three ZIF-67-derived nanostructured carbon materials, ZCNB has the highest adsorption capacity because of its high specific surface area, good wettability, high surface charge, and suitable pore sizes. Though the carbon nanotubes in the ZCNH and ZCNT could improve the electrical conductivity of the material, it leads to a decrease in the specific surface area and wettability, thereby reducing the adsorption capacity. This work would provide a reference for the design of MOFs-derived CDI electrode materials.

Cesium copper halides have attracted increasing attention for light-emitting diodes (LEDs) applications due to their high photoluminescence quantum efficiency (PLQE) and non-toxicity. However, the current film fabrication methods for copper halides cannot simultaneously meet the high-performance, eco-friendly, and good environmental tolerance requirements. Here, we demonstrate a facile approach that combines the advantages of both traditional nanocrystal-based methods and precursor solution-based methods. Through treating Cs₃Cu₂I₅ nanocrystal films with proper alcohols, Cs₃Cu₂I₅/CsCu₂I₃ mixed-dimensional copper halides are formed with enhanced PLQE and improved energy level matching. This enhances the peak EQE of copper halide LEDs to 0.8%, which is among the highest efficiency of lead-free metal halide nanocrystal LEDs. This work provides a new strategy for fabricating high-performance lead-free LEDs in an eco-friendly manner.

As one of the five major toxic elements, the health threat of arsenic to organisms and ecological environment has attracted serious public attention. As one of the important anthropogenic sources of arsenic, non-ferrous smelting, especially copper smelting, should be listed as a key concern. Therefore, clarifying the behavior of arsenic in the copper smelting process is of great significance to the normal production and environmental protection of copper smelting enterprises. This work briefly introduced the industrial copper minerals for smelting, the occurrence form of arsenic in copper ore, and the evolution of copper smelting process. Furthermore, the volatilization, transformation and distribution behavior of arsenic in representative copper smelting processes were analyzed to clarify its flow direction and enrichment law. The interactions between other mineral components (Cu, Pb, Zn, Fe, Ca, Si) and arsenic during the formation of smelting by-products (copper slag and flue dust) were investigated to elucidate the formation mechanism of arsenic pollutants. Finally, the control technologies for arsenic in smelting flue gas, flue dust and copper slag were analyzed to propose a possible future strategy to recover arsenic by converting arsenic pollutants to metallic arsenic.

Large-scale copper smelting bottom-blown furnace (BBF) plays an important role in the modern copper smelting industry. Compared with small and medium-sized BBFs, the characteristics of oxygen lances have changed greatly. Pneumatic mixing with the oxygen lance seat as a blowing unit has become a disturbance source in the furnace. The arrangement of the oxygen lance seat directly affects the smelting effect of large-scale BBF. This paper takes a large BBF in a smelter as the research object, establishes a local model based on the lance seat, and analyzes the influence of two oxygen lance seat parameters on the flow characteristics of the molten pool through computational fluid dynamics (CFD) numerical simulation. The results show that the lance seat angle and the distance between two oxygen lances have significant effects on the bubble floating path and the effective mixing zone range, respectively. Reducing the lance seat angle appropriately will extend the bubble floating movement space, and increasing the distance between two lances appropriately will weaken the overlap of the effective mixing zone. Rotating the furnace body or resetting oxygen lances is recommended, which is conducive to strengthening the smelting process of large BBF.

Although many technologies have been introduced to recover valuable metals from copper slags, their economic and environmental compatibilities were not satisfactory. The dissolution behaviors of metals from copper slag, were investigated at atmospheric pressure using hydrogen peroxide and acetic acid known as organic acid. The slag was a mixture of converter and flash furnace slag containing 6.74% Cu, 4.34 % Zn and 36.45% Fe. Conventional leaching experiments in atmospheric pressure were conducted in a 100 mL glass beaker using a teflon coated magnetic stirring bar in the magnetic stirrer. Under the optimum leaching conditions, the metal extractions of 98.04 % Cu, 28.8% Zn, and 2% Fe were obtained. The Raman spectroscopy revealed the presence of coordination of Cu²⁺/Zn²⁺ with AcO⁻ (acetate). The dissolution process was described by the first order kinetics equation. The apparent activation energy of 23.7 kJ/mol suggested that the dissolution process was under diffusion control. The reaction orders for H₂O₂ and CH₃COOH were established to be 1.24 and 0.1, respectively. The proposed new hydrometallurgical process method is simple, environmentally friendly and remarkably superior to other methods in terms of obtaining copper (II) acetate solution from copper slag under conventional conditions.

Herein, the flotation separation of dolomite and brucite was performed using tetrasodium hydroxyethylphosphate (TH) as the inhibitor. Microflotation tests show that for a sodium dodecyl sulfonate (SDS) concentration of 30 mg/L, 100 mg/L of TH can achieve the maximum flotation separation of 73.91% between brucite and dolomite. Moreover, the flotation recovery of dolomite is selectively reduced by a considerable amount. Detection results show that the wettability and charge of dolomite are higher than those of brucite owing to the selective adsorption of TH. Moreover, on the dolomite surface, the strong adsorption of TH interferes with SDS adsorption. Additionally, TH selectively binds to the exposed Ca sites on the dolomite surface, hindering SDS adsorption and resulting in poor dolomite floatability. The selective adsorption of TH on the dolomite surface enhances the flotation separation of dolomite and brucite.

To effectively separte pyrite from chalcopyrite, tetrazine thione group and hydrocarbon chain were combined to synthesize tetrazine thione collectors. The flotation performance of tetrazine thione collectors on chalcopyrite and pyrite was investigated, and the influence of different hydrophobic groups on the flotation performance was revealed. UV tests indicated that HxMTT was easy to bond with Cu⁺ and Cu²⁺, which accompanied by the release of H⁺ into solution, while HxMTT was not easy to bond with Fe²⁺ and Fe³⁺. AFM and contact angle measurements implied that HxMTT adsorption on chalcopyrite increased the surface hydrophobicity of chalcopyrite. The results of FTIR indicated HxMTT chemisorption on chalcopyrite surface, and XPS analysis further indicated HxMTT chemisorption on chalcopyrite surface by Cu—N and Cu—S bonds.

The primary goal of this study is to examine the flow of non-Newtonian Sutterby fluid conveying tiny particles as well as the induced magnetic field in the involvement of motile gyrotactic microorganisms. The flow is configured between a pair of circular disks filled with Sutterby fluid conveying tiny particles and gyrotactic microorganisms. The impact of Arrhenius kinetics and thermal radiation is also considered in the governing flow. The presented mathematical models are modified into nonlinear ordinary differential equations using the relevant similarity transformations. To compute the numerical solutions of nonlinear ordinary differential equations, the differential transform procedure (DTM) is used. For nonlinear problems, integral transform techniques are more difficult to execute. However, a polynomial solution is obtained as an analytical solution using the differential transform method, which is based on Taylor expansion. To improve the convergence of the formulated mathematical modeling, the Padé approximation was combined with the differential transformation method. Variations of different dimensionless factors are discussed for velocity, temperature field, concentration distribution, and motile gyrotactic microorganism profile. Torque on both plates is calculated and presented through tables.

The triple diffusion amalgamated with the convection occurs when the fluid flow is under the influence of two different densities with varied diffusion rates. The primary objective of this analysis is to compare hydrodynamic and hydromagnetic nanofluid flow over a horizontally placed plate for triple diffusive systems with mixed convection of quadratic nature. The additional novel features of the envisaged model are the consideration of variable thermal conductivity and nonlinear thermal radiative heat flux. The problem is comprised of a set of equations that are solved with the aid of the MATLAB bvp4c package. To visualize the impacts of the parameters with associated profiles, graphical illustrations are given. Graphs are utilized to evaluate how significant changes in the key parameters impact the related fields and their corresponding physical quantities. It is inferred that liquid velocity surges for numerous estimates of the Dufour parameter of salt 1 and salt 2. It is verified that the hydrodynamic flow is dominant in comparison to hydromagnetic. In addition, a comparison between the published results in a specific scenario and the current research is also included. An excellent correlation is attained.

This study presents an analytical solution for the electroosmotic flow of Casson fluid in a microchannel with non-uniformly charged walls. Our objective is to determine analytical expressions for velocity and volumetric flow rates in both sheared and unsheared regions of the microchannel, as well as to describe the stress and temperature distributions in these regions. Using the lubrication approximation, we reduce the governing equations of Casson fluid flow to their dimensionless forms, which we then solve analytically. We express velocities and volumetric flow rates analytically in both sheared and unsheared regions using the cosine function. Graphical representations show stress distribution, velocity distributions, flow rate distributions, and temperature distributions in the sheared and unsheared regions. Our findings reveal that there are variations in volumetric flow rate with respect to rising pressure gradients due to the opposite response of pressure gradient and flow rate compared to other parameters. Furthermore, we present graphical representations of temperature distributions with wall shape amplitude and joule heating. This analytical solution has significant implications for the design and optimization of microfluidic devices that use Casson fluids in various applications.

The influence of first order chemical reaction and thermal radiation on hydromagnetic heat and mass transport of power-law Carreau fluid flow via a convergent and divergent conduit due to heat source is investigated. A volumetric heat generating source and non-linear thermal radiation is considered for the fluid flow that is producing heat in the form of thermal radiation. The basic conservation equations including mass, momentum, energy, and species concentration in radial mode are reconstructed and solved numerically with RK-4 method based on the shooting simple algorithm. The model used for the existence of nanoparticles is the phenomenon model, considering the Brownian and thermophoresis of the particles. The momentum equation is assembled with Carreau model which extend the Jaffrey-Hamel problem. The effects of different power-law indices on thermal transmission due to fluid friction, heat, and mass transfer are primarily manifested in rheological properties, which elucidates that the shear-thickening fluids are more effective than the shear-thinning fluids. The rate of thermal transmission is found to be maximum on heat sources and minimum on maximizing the power law index. The investigations might aid in developing a method that is physically sound for systematizing assessments of fluid flow and energy use in contracting/expanding channels.

The unloading confining pressure tests were conducted on sandstone under the seepage pressure to reveal the relationships between the deformation characteristics and permeability and the stress paths and seepage pressure of the rock. The weights of influences of the confining pressure and seepage pressure on the damage of sandstone are quantified by symbolic statistics. Experimental results show that with the increasing confining pressure, the characteristic stress increases, and the growth rates of crack strain corresponding to the damage stress as well as the peak stress both decrease. However, with the increase of the seepage pressure, the characteristic stress decreases, the initial crack volumetric strain corresponding to the initiation stress reduces, the crack-growth volumetric strain corresponding to the damage stress increases and the growth rates of crack strain corresponding to the damage stress as well as the peak stress all increase. The permeability decreases slowly at first and then increases dramatically in the process of unloading confining pressure. Under the same confining pressure, the brittleness index and crack strain growth rates are the highest in the unloading test with seepage pressure, while they are moderate in the conventional unloading test, and the lowest in the loading test. The confining pressure is extremely correlated with the peak strength, axial strain, circumferential strain, crack circumferential strain corresponding to the peak strength. The seepage pressure is extremely correlated with growth rates of both crack axial strain and crack circumferential strain.

In the engineering related to seismic activities, such as shale gas extraction and EGS system, numerical simulation is a common research method. In current numerical simulations, the critical value of a variable (e.g., sliding velocity) is often set artificially to determine whether the element is destabilized, on which the seismic magnitude is calculated. This practice is highly subjective and arbitrary, which leads to inaccurate calculation results. In this paper, we propose a new method for calculating seismic magnitude based on the rate-state dependent friction law. Firstly, the sliding history of each element on the sliding surface is divided into stages, and then all elements in the coseismic stage are clustered in time and space. Finally, the seismic moment of an event is obtained by calculating the sum of the corresponding areas of the “cumulative slip-fault location” plot according to the clustering labels, which in turn gives the seismic magnitude.

In deep underground mining, high-stress condition plays a key role in rock blasting. However, the mechanism of rock breaking by blasting under high-stress conditions is still unclear. Therefore, crater blasting experiments and theoretical analyses were conducted to study the effect of in-situ stresses on rock fracturing. A 3D theoretical model considering stress concentration on the blasthole wall was conducted to further investigate the fracturing mechanism of crater blasting under in-situ stresses. The experimental and theoretical results allowed the following conclusions: 1) Long resistance line (over 6 cm) results in a decrease crater volume along with increasing confining pressure; 2) the influence of confining pressure on blasting gradually changes from negative restraining to positive promoting with decreasing resistance line (less than 5 cm); 3) Radial fracturing was restrained and the reflected tensile fracturing was promoted in the direction of higher in-situ stress. While, radial fracturing was promoted and the reflected tensile fracturing was restrained in the direction of lower in-situ stress. Reducing resistance line of crater blasting and increasing between spacing hole are the best to take advantage of the in-situ stress to promote the rock fragmentation by blasting.

In this paper, the uniaxial compression test of coking coal with different freeze-thaw (F-T) cycles was carried out, accompanied by the monitoring of the acoustic emission (AE) system and digital image correlation (DIC) system. The results show that with the increase of F-T cycles, there is the continuous increase and obvious development of the sample mass and the pore structure respectively, causing the deterioration of mechanical properties. In addition, the AE activity of the samples gradually increased, which is more obvious in the compaction stage; furtherly, the tensile microcracks in the rock during the compression test always account for a larger proportion (except for 30 F-T cycles). For the failure characteristics, the rock sample changes from splitting tensile failure to shear failure, and the fracture surface morphology changes from rough to smooth. The damage constitutive model of coking coal subjected to the F-T effect and axial load was established, which is in good agreement with the experiment results. Finally, it is found that the initial damage of coking coal subjected to F-T cycles could be attributable to the expansion of pore and fissure space caused by the freeze of free water, the increasingly enhanced water-rock interaction and the interaction between mineral particles.

Simplified rigid model of railway vehicles has been frequently utilized to examine train crashworthiness and to further optimize the energy distribution under a train collision. However, the effect of ignoring the elastic wave propagation on train crashworthiness performance is unclear. To address this limitation, a simplified one-dimensional elastic model is constructed and the effect of elastic wave propagation on energy absorption and dynamic characteristics of the train is investigated. Based on the classical elastic wave propagation theory, a law of scaling the density and elastic modulus accordingly to achieve the rod motion independence on its cross-sectional area is proposed. Then, the effect of elastic wave propagation speed on the energy absorption, stored elastic energy, and equilibrium velocity for a three-car-marshaling train collision under different impact velocities is discussed. It is found that the elastic wave propagation speed of approximately 3500 m/s has the best accordance with the real train model. The relative errors of absorbed energy of the simplified one-dimensional elastic model in comparison to that of the real train mode are only 2.56%, 1.84% and 1.45% under initial impact velocity 10 m/s, 15 m/s, 20 m/s, while the absorbed energy of the simplified rigid model is 10.7%, 12.4% and 14.8% higher than that of the real train model, illustrating that the rigid model significantly overestimates the absorbed energy. Our results can advance the crashworthiness design and optimization of the train under collisions.

To explore the propagation characteristics of elastic waves in a 3D periodic track structure and propose a vibration and noise control method, this paper adopts the 3D plane wave expansion method to establish a 3D periodic ballasted track structure model using the periodic structure theory, Timoshenko beam wave theory and the Mindlin plate-beam theory. The wave superposition method was used for hammer impact test to verify the correctness of the theoretical model. This model was used for elastic wave mode and parameter analysis of track structures. The generalized plane wave analytical method proposed in this paper was consistent with those measured experimentally in the wave superposition test. The results show that the proposed testing method was suitable for studying the dispersion characteristics of 3D periodic track structures. Increasing the ballast shear stiffness enhances the structure attenuation capacity in the gap frequency band; When the shear stiffness increases from 0.05 to 0.09 MN/mm, the band gap width reduction rate also increases from 0.06 to 0.21 Hz/MN. The width of the vibration attenuation frequency band is affected by the ballast mass with the maximum vibration attenuation at 500 kg. The condition for an abnormal Doppler effect can be obtained by changing the excitation frequency relative to and band gap frequency.

Exposed to crosswinds, dynamic response of the train and the guideway are the important aspects in the design of the high-speed maglev transit system. Firstly, the aerodynamic characteristics of a maglev vehicle were tested through a wind tunnel test. The proportional-integral-derivative-acceleration (PIDA) control algorithm, which combines a proportional-integral-derivative (PID) controller and acceleration feedback, was used to adjust the levitation and guidance control system of the maglev train. The spatial analysis model of the wind-static suspension-maglev train-guideway (WSMG) system and wind-moved maglev train-guideway (WMMG) were established. Subsequently, the influences of average wind, fluctuating wind, wind speeds, and vehicle speeds on the dynamic response of the maglev system were analyzed. The results indicate that the PIDA controller can eliminate the steady-state error of the magnetic gap caused by crosswinds. Compared with the PDA controller, the PIDA controller can reduce approximately 40% of the lateral displacement of the vehicle body. The average wind only changes the equilibrium position of the train, and the fluctuating winds and track irregularities are the significant cause for the vibration of the maglev train-guideway system. The lateral vibration of the vehicle is more sensitive to the wind velocity. The high-speed maglev train should stop running when the wind speed exceeds 30 m/s.

In the application of microscopic traffic simulations for vehicle emissions modeling, the reality and platoon stability of vehicle trajectories derived from the car-following component have been questioned. This study compared the platoon stability of the Gipps car-following model, the full velocity difference model (FVDM), the intelligent driver model (IDM), and the Wiedemann model for emissions modeling and proposed the modified Gipps model by incorporating stochastic parameters. The results indicated the superior performance of the FVDM and IDM for emissions estimation compared with the Wiedemann model, and the emissions estimation errors were stable along the platoon for the above models. Gipps model generated realistic vehicle dynamics of the first following vehicle; however, the emissions estimation errors increased along the platoon. After the optimization of the Gipps model by incorporating stochastic parameters, the root-mean-square error (RMSE) of acceleration distribution, RMSE of vehicle specific power (VSP) distribution and relative error of emission factor were reduced by 5.00%, 2.52% and 11.04%, respectively, and the standard deviations of the errors in the platoon were 0.18%, 0.08% and 0.86%, respectively. The stochastic parameters were proven to potentially improve the reality of simulated trajectory and the platoon stability of the Gipps model for accurate emissions modeling.

Connected and automated vehicles (CAVs) have great potential to improve driving safety. A basic performance evaluation criterion of CAVs is whether they can drive more safely than human drivers in real traffic scenarios. This study proposes a method to optimize longitudinal control model parameters of CAVs using empirical trajectory data of human drivers in risky car-following scenarios. Firstly, the initial car-following pairs (I-CFP) are extracted from empirical trajectory data. Then, two types of real longitudinal control models of CAVs, the adaptive cruise control (ACC) and the cooperative ACC (CACC) control models, are employed for simulation in the car-following scenarios with default parameter values, which generate original trajectories of simulated car-following pairs (S-CFP). Finally, a genetic algorithm (GA) is applied to optimize control model parameters of ACC and CACC vehicles and generate optimized trajectories of car-following pairs (O-CFP). Results indicate that safety condition of S-CFP is better than that of I-CFP, while the O-CFP has the best safety performance. The optimized parameters in the ACC/CACC models are diverse and different from the default parameters, indicating that the best model parameters vary with different car-following scenarios. Findings of this study provide a valuable perspective to reduce the rear-end collision risks.

Using the spatial and temporal characteristics of vehicle movement to analyze the control effect of the corridor progression, we can deeply explore the essential principle of progression design. Based on the progression design principle and the geometric elements’ transformation in the time–space diagram, a graphical optimization method for bidirectional corridor progression under the split phasing design is proposed. The initial comprehensive optimization determines the initial coordinated design scheme, and the iterative optimization re-optimizes the signal phase sequence, signal cycle, and offset. The case study shows that the proposed graphical method can quickly obtain a coordinated control scheme for the corridor with significant bandwidths in both directions. Simulation analysis using VISSIM shows that the proposed graphical method brings an optimal progression effect better than the PBAND method. The proposed method has a straightforward design process, a continuous optimization space, and a fast solution speed, which leads to its certain engineering application value.

The subway has increasingly taken over as the primary method of short-distance travel in the development of modern urban transportation. Due to the poor air mobility in subway stations, it is crucial to monitor and provide alerts on air quality. This work provides a probabilistic prediction framework of PM_2.5 concentration to solve the air quality early warning problem in subway stations. Firstly, outliers are discovered and corrected utilizing a probabilistic-based auto-encoder (PAE). Secondly, the multi-resolution elastic-gated attention mechanism is used to address error accumulation and historical information lost during the prediction process. Moreover, the decoder structure of sequence to sequence (Seq2Seq) is improved through multiple output strategy and flexible gate attention mechanism to reduce error accumulation. Finally, the Seq2Seq is equipped with Gaussian mixture models (GMM), allowing it to adapt to more complicated changes and produce a probability distribution of PM_2.5 concentrations. According to tests on data from subway stations, the Pinball loss and Winkler score of the proposed model are smaller compared to other models.