Siderite, as an abundant iron ore, has not been effectively utilized, with a low utilization rate. In this study, the in-situ kinetics and mechanism of siderite during suspension magnetization roasting (SMR) were investigated to improve the selective conversion of siderite to magnetite and CO, enriching the theoretical system of green SMR using siderite as a reductant. According to the gas products analyses, the peak value of the reaction rate increased with increasing temperature, and its curves presented the feature of an early peak and long tail. The mechanism function of the siderite pyrolysis was the contraction sphere model (R₃): f(α) =3(1 − α)^2/3; E_α was 46.4653 kJ/mol; A was 0.5938 s⁻¹; the kinetics equation was k=0.5938exp[− 46.4653/(RT)]. The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N₂ atmosphere. At 620 °C, the saturation magnetization (M_s), remanence magnetization (M_r), and coercivity (H_c) of the product peaked at 53.63×10⁻³ A·m²/g, 10.23× 10⁻³A×m²/g, and 12.40×10³ A/m, respectively. Meanwhile, the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process, which would contribute to reducing the grinding cost.

The integration of electronic components and the popularity of flexible devices have come up with higher expectations for the heat dissipation capability and comprehensive mechanical performance of thermal management materials. In this work, after the modification of polyimide (PI) fibers through oxidation and amination, the obtained PDA@OPI fibers (polydopamine (PDA)-modified pre-oxidized PI fibers) with abundant amino groups were mixed into graphene oxide (GO) to form uniform GO-PDA@OPI composites. Followed by evaporation, carbonization, graphitization and mechanical compaction, the G-gPDA@OPI films with a stable three-dimensional (3D) long-range interconnected covalent structure were built. In particular, due to the rich covalent bonds between GO layers and PDI@OPI fibers, the enhanced synergistic graphitization promotes an ordered graphitized structure with less interlayer distance between adjacent graphene sheets in composite film. As a result, the optimized G-gPDA@OPI film displays an improved tensile strength of 78.5 MPa, tensile strain of 19.4% and thermal conductivity of 1028 W/(m·K). Simultaneously, it also shows superior flexibility and high resilience. This work provides an easily-controlled and relatively low-cost route for fabricating multifunctional graphene heat dissipation films.

Inspired by the microstructure of gecko’s toe, two kinds of polyvinyl chloride (PVC) gels with different modulus were poured on a silicon mold with micropillars, and then a bio-inspired adhesive with variable modulus was manufactured in this study. The adhesions of variable modulus and fixed modulus bio-inspired adhesives were tested, respectively, on a smooth glass and a printed circuit board (PCB) with different surface structures. The results show that PVC gel bio-inspired adhesives with variable modulus have many advantages compared with the fixed modulus bio-inspired adhesives. The adhesion of variable modulus bio-inspired adhesives on the rough PCB surface increased by 2–5 times, and due to the use of variable modulus of PVC gel, the surface micropillars can maintain high aspect ratio and flexible tips at the same time. Moreover, the use of PVC gel makes it easier to demold during the bio-inspired adhesives preparation. An adhesion-desorption device was made according to the movement of the gecko toes, and the PCB was successfully grasped.

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising, green, and efficient power-generating devices that are fueled by solid carbons and comprise all-solid-state structures. Developing suitable anode materials for DC-SOFCs is a substantial scientific challenge. Herein we investigated the use of La_0.75Sr_0.25Cr_0.5Mn_0.5O_3−δ-Ce_0.8Gd_0.2O_1.9 (LSCM—GDC) composite electrodes as anodes for La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ electrolyte-based DC-SOFCs, with Camellia oleifera shell char as the carbon fuel The LSCM—GDC-anode DC-SOFC delivered a maximum power density of 221 mW/cm² at 800 °C and it significantly improved to 425 mW/cm² after Ni nanoparticles were introduced into the LSCM—GDC anode through wet impregnation The microstructures of the prepared anodes were characterized, and the stability of the anode in a DC-SOFC and the influence of catalytic activity on open circuit voltage were studied The above results indicate that LSCM—GDC anode is promising to be applied in DC-SOFCs.

In this study, non-equiatomic Fe₇₀Co_7.5Cr_7.5Ni_7.5V_7.5 medium-entropy alloys (MEAs) with different carbon contents were prepared via mechanical ball-milling, cold pressing and vacuum sintering. The microstructural evolution, mechanical properties and wear resistance of the MEAs were investigated Fe₇₀Co_7.5Cr_7.5Ni_7.5V_7.5 exhibited a body-centered cubic (bcc) structure with σ phase precipitation. After adding 4 at% and 8 at% carbon, the phase composition of the alloys was transformed to bcc+MC+ σ and bcc+MC+M₂₃C₆, respectively. The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides. Increasing the carbon content, the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4, respectively. Further, the dominant wear mechanism changed from the adhesion wear to the abrasion wear. Owing to the evenly distributed carbides and precipitated nanocarbides, Fe_64.4Co_6.9Cr_6.9Ni_6.9V_6.9C₈ revealed an extremely low specific wear rate of 1.3×10⁻⁶ mm²/(N·m) under a load of 10 N.

Ti-6Al-4V alloy powder was prepared through a two-step reduction of a mixture of TiO₂, V₂O₅ and Al₂O₃ in this study. The oxide mixture was first reduced by Mg in MgCl₂ at 750 °C in argon, where oxygen was reduced to 2.47 wt% from 40.02 wt%. The oxygen content in the final powder was eventually reduced to an extremely low level (0.055 wt%) using calcium at 900 °C in argon, and the final powder had the composition of 90.12 wt% Ti, 5.57 wt% Al, and 3.87 wt% V, which meets the standard specification of Ti-6Al-4V (ASTM F1108-09). Between the two reductions, a heat treatment step was designed to help controlling the specific surface area and particle size. The effect of the heat treatment temperature on the morphology, and composition uniformity of the powder was investigated in detail. Heat treatment above 1300 °C attributed to a dense powder with a controlled specific surface area. Thermodynamic modeling and experimental results indicated that only α-Ti enriched with Al and β-Ti enriched with V exist in the final powder, and other possible phases including Al-Mg and Al-V were excluded. This study also offers a triple-step thermochemical process for producing high-purity Ti-based alloy powder.

Porous materials can be found in a variety of geophysical and engineering applications. The existence of thermal contact resistance at the interface between bilayered saturated porous strata would result in a significant temperature difference at the interface. An attempt is made to study the thermo-hydro-mechanical coupling dynamic response of bilayered saturated porous strata with thermal contact resistance and elastic wave impedance. The corresponding analytical solutions for the dynamic response of bilayered saturated porous strata under a harmonic thermal load are derived by the operator decomposition method, and their rationality is verified by comparing them with existing solutions. The influences of thermal contact resistance, thermal conductivity ratio, and porosity ratio on the dynamic response of bilayered saturated porous strata are systematically investigated. Outcomes disclose that with the increase of thermal contact resistance, the displacement, pore water pressure and stress decrease gradually, and the temperature jump at the interface between two saturated porous strata increases.

Coal mine fires, which can cause heavy casualties, environmental damages and a waste of coal resources, have become a worldwide problem. Aiming at overcoming the drawbacks, such as a low analysis efficiency, poor stability and large monitoring error, of the existing underground coal fire monitoring technology, a novel monitoring system based on non-dispersive infrared (NDIR) spectroscopy is developed. In this study, first, the measurement principle of NDIR sensor, the gas concentration calculation and its temperature compensation algorithms were expounded. Next, taking CO and CH₄ as examples, the liner correlation coefficients of absorbance and the temperature correction factors of the two indicator gases were calculated, and then the errors of concentration measurement for CO, CO₂, CH₄ and C₂H₄ were further analyzed. The results disclose that the designed NDIR sensors can satisfy the requirements of industrial standards for monitoring the indicator gases for coal fire hazards. For the established NDIR-based monitoring system, the NDIR-based spectrum analyzer and its auxiliary equipment boast intrinsically safe and explosion-proof performances and can achieve real-time and in-situ detection of indicator gases when installed close to the coal fire risk area underground. Furthermore, a field application of the NDIR-based monitoring system in a coal mine shows that the NDIR-based spectrum analyzer has a permissible difference from the chromatography in measuring the concentrations of various indicator gases. Besides, the advantages of high accuracy, quick analysis and excellent security of the NDIR-based monitoring system have promoted its application in many coal mines.

Magnetite is a kind of iron ore that is difficult to carburize. In order to improve the carburizing performance of magnetite pellet, pre-oxidation treatment was carried out, and the oxidation, reduction and carburization behaviors of magnetite pellet were investigated in this study. The magnetite pellet was oxidized in the air and carburized in CO-CO₂-H₂ gas mixtures, the oxidation, reduction and carburization behaviors were demonstrated by detecting phase change, microstructure, carburizing index via thermogravimetry, X-ray diffraction (XRD), infrared carbon-sulfur analyzer, and scanning electron microscope (SEM). The results show that the dense magnetite particles inside pellet are oxidized to porous hematite particles, and the Fe₃O₄ transforms to Fe₂O₃ with high lattice defect concentration during the pre-oxidation process. Then the porous hematite particles and newly formed Fe₂O₃ significantly promote the reduction efficiency. Porous metallic iron particles are produced in the reduction process. Finally, both high reduction efficiency and the porous structure of metallic iron particles dramatically enhance the carburization efficiency of pellet. High pre-oxidation temperature favors to the carburization of magnetite pellet. However, the carburized index decreases due to the recrystallization of iron oxide when the temperature extends to 1000 ° C. The optimum pre-oxidation temperature for magnetite pellet carburization is 900 °C.

Phosphogypsum (PG) is a potential resource for rare earth elements (REEs). Several studies have been carried out on REE leaching from PG. However, few in-depth studies have investigated the kinetics of this leaching process. In this study, the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth. The experiments show that the maximum leaching recovery for ς REE was 58.5%, 75.9% and 83.4% at 30, 60 and 80 °C, respectively. Additionally, among La, Ce, Y and Nd, Y had the highest leaching rate. A new shrinking core model (SCM) based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG. The activation energies for the leaching of La, Ce, Y and Nd were determined on the basis of the new cylindrical SCM. In summary, the cylindrical SCM was a more suitable fitting model than the spherical SCM, and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.

The present study aims at the recovery of potassium from muscovite mica (which contains K₂O; ~10 wt%) using NaCl-roasting coupled with H₂SO₄-leaching process. The preliminary acid leaching studies applying different mineral acids resulted in a potassium recovery of 8%–18%. The optimum leaching conditions for the maximum recovery were 4 mol/L H₂SO₄, 60 min leaching time and liquid-solid ratio 4 mL/g at 90 °C. However, the roasting of muscovite with additive NaCl (muscovite: NaCl mass ratio of 1:1.00, 900 °C, 45 min) followed by H₂SO₄-leaching (95 °C, 60 min) extracted potassium to the tune of 98%. Under similar roasting conditions, the H₂O-leaching process extracted only 60% of potassium. The effects of various roasting and leaching parameters such as temperature, time, NaCl concentration, acid concentration, liquid-solid ratio on potassium extraction were evaluated. The appearance of the sylvite (KCl) mineral phase in the NaCl-roasted muscovite and its disappearance in the acid/water leached residue confirmed the physical and chemical distortions of the muscovite crystal structure. The possible mechanism of potassium release from the complex muscovite structure was elucidated based on available literature substantiated by characterizations using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-rays spectroscopy (SEM-EDX).

for non-quenchable dual-phase (DP) steel sheet, the warm forming process can effectively reduce the amount of springback, and the mechanical parameters that influence its elastic and inelastic recovery to decrease exhibit a strong temperature dependence, especially under cyclic loading conditions. In this paper, the monotonic and cyclic loading tests of DP980 steel sheets are conducted at the temperatures ranging from 25 °C to 500 °C. The temperature-dependent flow stress, nonlinear elastic recovery, and Bauschinger effect are investigated. The results demonstrate that both the elastic modulus and Bauschinger effect show an exponential law with pre-strain, and decrease with the increase of forming temperature, while there will be an abnormal phenomenon of rebound due to the influence of dynamic strain aging effect. Meanwhile, a linear relationship between the Bauschinger effect and inelastic strain is observed at various temperatures, and the weight of the Bauschinger effect in the total strain reduces with temperature increasing, which indicates that the springback is dominated by linear elastic recovery. Furthermore, the U-draw bending tests are carried out to clarify the influence of Vickers hardness distribution and martensite size effect on the springback behavior.

The heat generation behaviors of fatigue crack are deeply investigated under different preload forces combing numerical simulation and experiment. Firstly, a multi-contact simulation model is applied to stimulate the crack surfaces contact and the horn-sample contact under ultrasonic excitation for calculating the temperature fields. Then, the ultrasonic infrared thermography testing and the microscope testing are carried out for the heat generation and the plastic deformation behaviors of crack region under different preload forces. On this basis, an indirect observation method based on dots distribution is proposed to estimate the plastic deformation on crack contact surfaces. The obtained results show that the temperature rise of crack region increases with the increase of preload force when the preload force is less than 250 N, while the temperature rise rapidly declines due to the plastic deformation on crack contact surfaces and the inhibition effect when the preload force is 280 N. Moreover, the plastic deformation does not lead to the crack propagation, but reduces the detection repeatability of fatigue crack. This work provides an effective method for optimizing testing conditions in practical testing processes, which will be helpful to the establishment of testing standards for batches of test objects in ultrasonic infrared thermography testing.

The complexity of a rock masses structure can lead to high uncertainties and risk during underground engineering construction. Laboratory tests on fractured rock-like materials containing a tunnel were conducted, and two-dimensional particle flow models were established. The principal stress and principal strain distributions surrounding the four-arc-shaped and inverted U-shaped tunnels were investigated, respectively. Numerical results indicated that the dip angle combination of preexisting fractures directly affects the principal stress, principal strain distribution and the failure characteristics around the tunnel. The larger the absolute value of the preexisting fracture inclination angle, the higher the crushing degree of compression splitting near the hance and the larger the V-shaped failure zone. With a decrease in the absolute value of the preexisting fracture inclination angle, the compressive stress concentration of the sidewall with preexisting fractures gradually increases. The types of cracks initiated around the four-arc-shaped tunnel and the inverted U-shape tunnel are different. When the fractures are almost vertical, they have a significant influence on the stress of the sidewall force of the four-arc-shaped tunnel. When the fractures are almost horizontal, they have a significant influence on the stress of the sidewall of the inverted U-shaped tunnel. The findings provide a theoretical support for the local strengthening design of the tunnel supporting structure.

The advance speed of the working face in coal mines can significantly affect the fluctuation frequency of abutment pressure in front of the coal body. Moreover, it has a certain correlation with the change of axial loading rate in coal and rock mechanics test. Therefore, uniaxial compression tests under various loading rates of 0.05, 0.1, 0.15, 0.25, 0.5 MPa/s were conducted using 2000 kN triaxial testing machine and PCI-2 acoustic emission test system to study the loading rate effect on the mechanical properties of deep sandstones. The results show that 1) the peak strength and elastic modulus of the deep sandstone increase with the loading rate increasing; 2) with the loading rate increasing, the deep sandstone transforms from plastic-elastic-plastic to plastic-elastic and moreover, the failure mode gradually transfers from type I to type III; 3) With the loading rate increasing, the total input strain energy, elastic strain energy, and dissipated strain energy generally increase; 4) the damage variable presents the evolution characteristics of inverted “S” shape with time, and with the loading rate increasing, the damage degree of the deep sandstone is aggravated. The conclusion obtained can provide the theoretical basis for the stability control of the surrounding rock in deep engineering.

Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering. Basalt fiber is a new kind of environment-friendly and high-performance soil reinforcement material, and the mechanical properties of basalt fiber-reinforced soil have become a hot research topic. In this paper, we conducted monotonic triaxial and cyclic triaxial tests, and analyzed the influence of the fiber content, moisture content, and confining pressure on the shear characteristics, dynamic modulus, and damping ratio of basalt fiber-reinforced silty clay. The results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its cohesion. We find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2% and the moisture content is 18.5% (optimum moisture content). Similarly, we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2% and the moisture content is 18.5%. The dynamic modulus is positively correlated with the confining pressure. However, the change in the damping ratio with fiber content, moisture content, and confining pressure is opposite to that of the dynamic modulus. It can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%. After our experiments, we used scanning electron microscope (SEM) to observe the microstructure of specimens with different fiber contents, and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.

In China, Beishan granite is chosen as a potential host surrounding rock of a high-level radioactive waste (HLW) repository. For this research, Beishan granite specimens were heated up to 300 °C, 400 °C and 500 °C, respectively. And conventional triaxial compression tests were conducted after cooling down the samples. The results show that after 300 °C, 400 °C and 500 °C heating treatment, the diameter of samples increases by 0.066%, 0.143% and 0.409%, respectively, which is a little larger than the axial length changes. Mechanical tests show that peak strength increases slightly with increasing temperature. However, the dilatancy threshold is lower than that observed for samples which have not experienced heating treatment. Peak strain and dilatancy threshold strain show a strong temperature dependence. The higher the temperature, the greater the strain. Furthermore, increasing temperature has negative influence on threshold elastic modulus E_c and tangent elastic modulus E_t. Poisson ratio decreases when temperature increases from 300 °C to 500 °C, but it is still larger than that observed for samples which have not experienced heating treatment. In addition, AE monitoring shows a quiet period in the initial loading stage, which proves that the micro cracks are closed during heating and contribute to the increase of peak strength.

The landslide disaster caused by the argillaceous interlayer not only destroys buildings, cultivated land, and roads but also seriously endangers human life and safety. This study concerns the mineral composition of selected argillaceous interlayer and their strength characteristics. To study the mineral composition of argillaceous interlayers, 8 kinds of samples in the southern Jiangsu region of China were analyzed utilizing X-ray diffraction (XRD). The repeated direct shear strength tests (RDST) were carried out on the undisturbed specimens of the argillaceous interlayer. The results show that the argillaceous interlayer with high content of kaolinite shows ductile failure mode, which means that there is no obvious residual strength in the shear process. The arrangement of mineral particles on the shear surface of the specimens after different shear displacements was observed under the scanning electron microscope (SEM). It was observed that mineral particles on the shear surface showed a more directional arrangement with the increase of shear displacement. Furthermore, the influence of shear direction on the argillaceous interlayer with completely oriented mineral particles was studied through numerical experiments with four shear strength mechanisms proposition proposed. The influence of the mineral arrangement on the action occasion and magnitude of dilatancy component of shear strength is clarified in the shear mechanism.

With the high-quality development of urban buildings, higher requirements are come up with for lateral bearing capacity of laterally loaded piles. Consequently, a more accurate analysis to predict the lateral response of the pile within an allowable displacement is an important issue. However, the current p-y curve methods cannot fully take into account the pile-soil interaction, which will lead to a large calculation difference. In this paper, a new analytical p-y curve is established and a finite difference method for determining the lateral response of pile is proposed, which can consider the separation effect of pile-soil interface and the coefficient of circumferential friction resistance. In particular, an analytical expression is developed to determine the compressive soil pressure by dividing the compressive soil pressure into two parts: initial compressive soil pressure and increment of compressive soil pressure. In addition, the relationship between compressive soil pressure and horizontal displacement of the pile is established based on the reasonable assumption. The correctness of the proposed method is verified through four examples. Based on the verified method, a parametric analysis is also conducted to investigate the influences of factors on lateral response of the pile, including internal friction angle, pile length and elastic modulus of pile.

Deformation and failure of deep clay samples are closely related to energy changes. Investigating the energy conversion and damage behavior of deep clay during loading and unloading tests has important significance for prevention-control of soil destabilization damage caused by mine shaft excavation. In the present work, triaxial tests of consolidated clay under different stress paths and stress rates were conducted. The results reveal that the mechanical properties of soils have strong stress rate effects and the samples mainly experience energy storage in the elastic stage, after that, the energy conversion mainly undergoes an increase of dissipative energy and release of elastic energy, which is also confirmed by the results of the analysis in the subsequent CT tests. Two damage indicators were compared, finding that the indicator based on dissipative energy has more obvious differences in two stress paths and can be used as a better indicator to describe the damage evolution of soils. Finally, in the triaxial shear test, due to the unloading effect of confining pressure, the damage of soils increased more rapidly near breaking than in the triaxial compression test, which indicates that the damage caused by unloading on deep soil is more abrupt than that caused by loading.

A filter cake is often formed between soil and concrete during casting concrete in the ground, such as constructions of diaphragm walls and bored piles. The present study aims to investigate the effect of the filter cake on the shear behavior of the sand-concrete pile interface. A series of sand-concrete interface direct shear tests were performed with a large-direct shear apparatus while considering different roughness (I=0, 10, 20 and 30 mm) and filter cake thickness (∆h=0, 5 and 10 mm). For a smooth interface without a filter cake, the shear stress-horizontal displacement curves showed a “softening” response. The peak shear strength and friction angle decreased exponentially with increasing the ∆h. Whereas, for a rough interface with ∆h=5 or 10 mm, the shear stress-horizontal displacement curves presented a “hardening” response. The peak strength, as well as friction angle, decreased linearly with increasing the ∆h. Moreover, a critical roughness I_cr of 10 mm was observed in the tests without a filter cake. The interface shear strength initially increased with increasing I but gradually decreased when the I exceeded I_cr. In addition, the filter cake could reduce the roughness sensitivity on shear strength.

This paper presents an analytical procedure for massive water-sealing barriers (MWSBs) that are made of partially overlapped jet-grouting columns used for deep excavations, in which two crucial factors of the permeability and strength of jet-grouted materials are considered. Subsequently, a calculation example is analyzed and discussed. Results show that “tension failure” mechanism is a major concern for the structural failure during a design of MWSBs. The maximum allowable seepage discharge is a crucial index for the design of MWSBs, which has a significant influence on determining the design parameters of MWSBs. Compared with the design procedure for MWSBs that is proposed in this paper, the design parameters of MWSBs determined by the stability equilibrium and seepage stability equilibrium approaches are conservative due to the fact that it fails to consider the permeability or strength of jet-grouted materials that makes a contribution to the structural safety. Based on the proposed design method, the ranges of both the thickness and depth of MWSBs for a case history of subway excavation in Fuzhou, China were determined. Finally, field pumping test results showed that the water-tightness performance of MWSBs performed at site was quite well.

Considering the fact that in some complex cases, plate anchors are buried in multi-layered geotechnical materials, the ultimate dynamic analysis was performed to investigate the uplift capacity and failure mechanism of shallow strips and circular plate anchors in multi-layered soils. The nonlinear strength criterion and non-associated flow rule of geotechnical materials were introduced to investigate the influence of nonuniformity on the pullout performance and failure mechanism of shallow plate anchors. The expressions of the detaching curves or surfaces were obtained to reflect the failure mechanism, which can be used to figure out the ultimate uplift capacity and failure range. The results are generally in agreement with the numerical simulations and previous research. The effects of various parameters on the ultimate uplift capacity and failure mechanism of plate anchors in multi-layered soils were investigated, and it is found that the ultimate uplift capacity and failure range of shallow anchors increase with the increase of initial cohesion and dilatancy coefficient, but decrease with the unit weight, axial tensile stress and nonlinear coefficient.

The effects of different yaw angles on the aerodynamic performance of city electric multiple units (EMUs) were investigated in a wind tunnel using a 1:16.8 scaled model. Pressure scanning valve and six-component box-type aerodynamic balance were used to test the pressure distribution and aerodynamic force of the head car respectively from the 1.5- and 3-coach grouping city EMU models. Meanwhile, the effects of the yaw angles on the pressure distribution of the streamlined head as well as the aerodynamic forces of the train were analyzed. The experimental results showed that the pressure coefficient was the smallest at the maximum slope of the main shape-line. The side force coefficient and pressure coefficient along the head car cross-section were most affected by crosswind when the yaw angle was 55°, and replacing a 3-coach grouping with a 1.5-coach grouping had obvious advantages for wind tunnel testing when the yaw angle was within 24.2°. In addition, the relative errors of lift coefficient C_L, roll moment coefficient C_Mx, side force coefficient C_S, and drag coefficient C_D between the 1.5- and 3-coach cases were below 5.95%, which all met the requirements of the experimental accuracy.

PM_2.5 forecasting technology can provide a scientific and effective way to assist environmental governance and protect public health. To forecast PM_2.5, an enhanced hybrid ensemble deep learning model is proposed in this research The whole framework of the proposed model can be generalized as follows: the original PM_2.5 series is decomposed into 8 sub-series with different frequency characteristics by variational mode decomposition (VMD); the long short-term memory (LSTM) network, echo state network (ESN), and temporal convolutional network (TCN) are applied for parallel forecasting for 8 different frequency PM_2.5 sub-series; the gradient boosting decision tree (GBDT) is applied to assemble and reconstruct the forecasting results of LSTM, ESN and TCN. By comparing the forecasting data of the models over 3 PM_2.5 series collected from Shenyang, Changsha and Shenzhen, the conclusions can be drawn that GBDT is a more effective method to integrate the forecasting result than traditional heuristic algorithms; MAE values of the proposed model on 3 PM_2.5 series are 1.587, 1.718 and 1.327 µg/m³, respectively and the proposed model achieves more accurate results for all experiments than sixteen alternative forecasting models which contain three state-of-the-art models.

In this work, the efficiency of an adsorption process, in which Moroccan diatomite (ND) is used as a low-cost adsorbent to remove Congo red (CR) dye from contaminated waters in batch and column system, was examined. The influence of experimental conditions (pH, adsorbent dose and temperature) on the adsorption of CR onto the ND adsorbent was studied. A study of the adsorption kinetics for CR revealed that a pseudo-second-order model provided the best fit to the experimental kinetic data, and the equilibrium data were well described by the Langmuir isotherm model with an adsorption capacity of 6.07 mg/g using 15 g/L of ND, pH=6, contact time 3 h and 25 °C. On the other hand, the ND regeneration tests were investigated and showed that the desorption reaches at least 50% when using ethanol as eluent. In addition, the adsorption process in a continuous mode was studied. Breakthrough curves were properly represented by the Yoon — Nelson model. Hence, the adsorption capacity of 5.71 mg/g was reached using 0.114 g of adsorbent, CR concentration of 6 mg/L and a flow of 1 mL/min under 25 °C.