Given the increasing use of glass mat-reinforced thermoplastic (GMT) composites, the formability of GMT sheets is currently a topic of research. A new sheet forming process for solidified GMT was developed. In this process, a GMT sheet was sandwiched by dummy metallic sheets during deep drawing. The dummy metallic sheets acted as protective materials and media for heating the GMT sheet. In this study, tensile tests of GMT specimens were carried out under different temperature conditions. The effect of temperature on the tensile deformation was analyzed. The effect of temperature on the deep drawing process of GMT sheets with dummy sheets was further investigated. Finite element method (FEM) was conducted to simulate the deep drawing process. In the drawing force rising stage, the law of drawing force with the depth of the drawing was analyzed using FEM and experiments.

The composition of a collector directly affects its collecting performance in mineral flotation. In this study, three vegetable oils were used as the collectors, the flotation performance of scheelite and the differential analysis were studied through flotation experiments, zeta potential, contact angle measurement and Fourier transform infrared spectrum (FTIR) analysis. Flotation results show that the recovery of scheelite increases in the order of oleic acid<rapeseed oil<rice bran oil<soybean oil, especially in the pH range of 5–8. The distinction in the scheelite recovery is due to the different compositions of these collectors. The addition of LA, LNA and PA (<5%) can increase the recovery of scheelite with OA, but the addition of SA deteriorates the scheelite flotation. Results of zeta potential, contact angle measurement and FTIR analysis indicate that the collector adsorption on scheelite surface is enhanced when using the three vegetable oils. For the raw ore with 0.086% WO₃, a rough concentrate containing 1.423% WO₃ with the recovery of 84.22% is obtained using soybean oil as the collector.

The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated. Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe³⁺/Fe²⁺ couple and material exchange. The passivation of iron settling correlates with ferrous ion content in bio-leaching solution. In medium containing A. ferrooxidans and Fe(III), the increment in Fe(II) concentration leads to the formation of jarosite, generating a decline in vanadium extraction efficiency. Analysis of cyclic voltammetry shows that Fe(II) ion is apt to be oxidized and translated into precipitate by A. ferrooxidans, which strongly adsorbed to the surface of the residue. Fe(III) ion promotes the vanadium extraction due to its oxidizing activity. Admixing A. ferrooxidans to Fe(III) medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution. This motivates 3.8% and 21.8% increments in recovery ratio and leaching rate of vanadium compared to the Fe(III) exclusive use, respectively. Moreover, Fe(II) ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.

Flotation is often employed to separate valuable natural minerals and gangue minerals. However, few studies have been conducted on artificial mineral flotation. Anosovite, the primary mineral in titanium slag, is a typical artificial mineral that can be enriched by flotation. In the present work, flotation behavior and adsorption mechanism of anosovite in salicylhydroxamic acid (SHA) solution were studied. The influence of pH and SHA dosage on anosovite flotability was investigated. Micro-flotation test results show that a pH range of 7–8.5 is available for SHA to collect anosovite. A maximum recovery of 93.26% can be obtained with SHA dosage of only 4×10⁻⁵ mol/L. In addition, TOC, zeta potential, FTIR, SEM-EDS, and XPS analyses were used to study the adsorption mechanism. Results demonstrated that SHA adsorption is governed by chemisorption. XPS studies further suggested that chemical adsorption occurred at the Ti sites on the anosovite surface.

A novel three-dimension (3D) graphene/MgO composite was synthesized through self-assembly and embedding MgO nanoparticle in reduced graphene in situ. Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), powder X-raydiffraction (XRD) and X-rayphotoelectron spectroscopy(XPS) were employed to characterize the prepared 3D graphene/MgO composite. The adsorption performance of some metal ions on 3D graphene/MgO was investigated. The results showed that the adsorption capacity was greater than 3D graphene and the maximum adsorption capacity at 25 °C was found to be 358.96 mg/g, 388.4 mg/g and 169.8 mg/g for Pb²⁺, Cd²⁺ and Cu²⁺, respectively. The adsorption kinetic conformed to the pseudo-second-order kinetic model and the adsorption isotherm was well described by Langmuir model. The thermodynamic constants revealed that the sorption process was endothermic and spontaneous in nature. Based on the results of the removal of heavy metal ions from metal smelting wastewater, it can be concluded that the prepared 3D graphene/MgO composite is an effective and potential adsorbent.

The impulsive components induced by bearing faults are key features for assessing gear-box bearing faults. However, because of heavy background noise and the interferences of other vibrations, it is difficult to extract these impulsive components caused by faults, particularly early faults, from the measured vibration signals. To capture the high-level structure of impulsive components embedded in measured vibration signals, a dictionary learning method called shift-invariant K-means singular value decomposition (SI-K-SVD) dictionary learning is used to detect the early faults of gear-box bearings. Although SI-K-SVD is more flexible and adaptable than existing methods, the improper selection of two SI-K-SVD-related parameters, namely, the number of iterations and the pattern lengths, has an adverse influence on fault detection performance. Therefore, the sparsity of the envelope spectrum (SES) and the kurtosis of the envelope spectrum (KES) are used to select these two key parameters, respectively. SI-K-SVD with the two selected optimal parameter values, referred to as optimal parameter SI-K-SVD (OP-SI-K-SVD), is proposed to detect gear-box bearing faults. The proposed method is verified by both simulations and an experiment. Compared to the state-of-the-art methods, namely, empirical model decomposition, wavelet transform and K-SVD, OP-SI-K-SVD has better performance in diagnosing the early faults of a gear-box bearing.

The ongoing need for better fuel economy and lower exhaust pollution of vehicles has increased the employment of electric power steering (EPS) in automotives. Optimal design of EPS for a product family reduces the development and fabrication costs significantly. In this paper, the TOPSIS method along with the NSGA-II is employed to find an optimum family of EPS for an automotive platform. A multi-objective optimization problem is defined considering road feel, steering portability, RMS of Ackerman error, and product family penalty function (PFPF) as the conflicting objective functions. The results for the single objective optimization problems and the ones for the multi-objective optimization problem, as well as two suggested trade-off design points are presented, compared and discussed. For the two suggested points, performance at one objective function is deteriorated by about 1%, while the commonality is increased by 20%–40%, which shows the effectiveness of the proposed method in first finding the non-dominated design points and then selecting the trade-off among the obtained points. The results indicate that the obtained trade-off points have superior performance within the product family with maximum number of common parts.

This study was conducted to investigate the flow field characteristics of right-angled flow passage with various cavities in the typical hydraulic manifold block. A low-speed visualization test rig was developed and the flow field of the right-angled flow passage with different cavity structures was measured using 2D-PIV technique. Numerical model was established to simulate the three-dimensional flow field. Seven eddy viscosity turbulence models were investigated in predicting the flow field by comparing against the particle image relocimetry (PIV) measurement results. By defining the weight error function K, the S-A model was selected as the appropriate turbulence model. Then, a three-factor, three-level response surface numerical test was conducted to investigate the influence of flow passage connection type, cavity diameter and cavity length-diameter ratio on pressure loss. The results show that the Box-Benhnken Design (BBD) model can predict the total pressure loss accurately. The optimal factor level appeared in flow passage connection type II, 14.64 mm diameter and 67.53% cavity length-diameter ratio. The total pressure loss decreased by 11.15% relative to the worst factor level, and total pressure loss can be reduced by 64.75% when using an arc transition right-angled flow passage, which indicates a new direction for the optimization design of flow passage in hydraulic manifold blocks.

This article gives a numerical report to two dimensional (2D) Darcy-Forchheimer flow of carbon-water nanofluid. Flow is instigated by exponential extending curved surface. Viscous liquid in permeable space is described by Darcy-Forchheimer. The subsequent arrangement of partial differential equations is changed into ordinary differential framework through proper transformations. Numerical arrangements of governing frameworks are set up by NDSolve procedure. Outcomes of different sundry parameters on temperature and velocity are examined. Skin friction and heat transfer rate are also shown and inspected.

Based on heat and mass transfer characteristics of spontaneous combustion of coal, Arrhenius equation and the Ranz-Marshall correlation, a novel approach was proposed in this paper to estimate oxygen consumption rate of self-ignition of coal at high temperature. Compared with the conventional methods, this approach involves not only kinetic properties of self-ignition of coal and temperature, but also the ambient air flow characteristics and diameter of coal particle. To testify the proposed approach, oxygen consumption rates at high temperature were measured by the programmable isothermal oven experiments. Comparisons between experimental and theoretical results indicate that the rates of oxygen depletion calculated by the proposed approach agree well with those measured from laboratory-scale experiments, which further validates the proposed approach.

A robust sliding mode control algorithm is developed for a class of networked control system with packet dropouts in both sensor-controller channel and controller-actuator channel, and at the same time mismatched parametric uncertainty and external disturbance are also taken into consideration. A two-level Bernoulli process has been used to describe the packet dropouts existing in both channels. A novel integral sliding surface is proposed, based on which the H_∞ performance of system sliding mode motion is analyzed. Then the sufficient condition for system stability and robustness is derived in the form of linear matrix inequality (LMI). A sliding mode controller is designed which can guarantee a relatively ideal system dynamic performance and has certain robustness against unknown parameter perturbations and external disturbances. The results from numerical simulations are presented to corroborate the validity of the proposed controller.

Autonomous vehicle technology will transform fundamentally urban traffic systems. To better enhance the coming era of connected and autonomous vehicles, effective control strategies that interact wisely with these intelligent vehicles for signalized at-grade intersections are indispensable. Vehicle-to-infrastructure communication technology offers unprecedented clues to reduce the delay at signalized intersections by innovative information-based control strategies. This paper proposes a new dynamic control strategy for signalized intersections with vehicle-to-signal information. The proposed strategy is called periodic vehicle holding (PVH) strategy while the traffic signal can provide information for the vehicles that are approaching an intersection. Under preliminary autonomous vehicle (PAV) environment, left-turning and through-moving vehicles will be sorted based on different information they receive. The paper shows how PVH reorganizes traffic to increase the capacity of an intersection without causing severe spillback to the upstream intersection. Results show that PVH can reduce the delay by approximately 15% at a signalized intersection under relatively high traffic demand.

An EMU train with detailed cabin structural is established based on the finite element method. The secondary impact between train driver and control desk is fully analysed and two measures are proposed to reduce the driver injury severity, such as the multi-objective optimization of the driver seat position and equipping the train with three-point seat belt. Simulation results indicate that the driver seat position has a significant effect on the driver injury severity during a secondary impact. According to the multi-objective optimization, some Pareto solutions are suggested to design the driver seat position. Besides that, it is also indicated although the chest and leg are well protected when the driver wears a two-point seat belt, it increases the head injure during a secondary impact. On the other hand, the three-point seat belt can supply the train driver with an overall protection against the secondary impact. The injury criteria (HIC, VC, TI) of the driver with the three-point seat belt is significantly lower than those of the driver without seat belt. Moreover, according to the simulation analysis, the limited load of the three-point seat belt is suggested about 1.5 kN.

Failure analysis of railway draw-hook coupler was carried out. The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler. Draw-Hook coupler is used to connect with the same hook coupler or automatic coupler. The influence of each connection types on the coupler strength in this study was discussed. A numerical stress analysis using FEM was performed, and many approaches including critical plane approach were carried out on fatigue life prediction of coupler under different conditions. The results of the proposed fatigue criterion and fatigue life predictions, as well as static numerical analysis, are validated with experimental results.

Caprocks play an important role in the trapping of coalbed methane (CBM) reservoirs. To study the sealing capacities of caprocks, five samples with different lithologies of Neogene clayrock, Paleogene redbeds, Permian sandstone, Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation, pore structure measurement and diffusion properties determination. Results indicate that with denser structures, lower porosities, much more developed micropores/transition pores and higher pore/throat ratios, mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks; the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds. To further estimate the CBM escape through caprocks, a one-dimensional CBM diffusion model is derived. Modeling calculation result demonstrates that under the same thickness, the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds, and nearly 17 times higher than sandstone, which indicates that the coal seam below caprocks like clayrock, redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone. Such conclusion is verified by the case study from III3 District, Xutuan Colliery, where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone, siltstone and sandstone.

A small problem about soil particle regularization and contacts but essential to geotechnical engineering was studied. The soils sourced from Guangzhou and Xiamen were sieved into five different particle scale ranges (d< 0.075 mm, 0.075 mm≤d<0.1 mm, 0.1 mm≤d<0.2 mm, 0.2 mm≤d<0.5 mm and 0.5 mm≤d<1.0 mm) to study the structures and particle contacts of granite residual soil. The X-ray micro computed tomography method was used to reconstruct the microstructure of granite residual soil. The particle was identified and regularized using principal component analysis (PCA). The particle contacts and geometrical characteristics in 3D space were analyzed and summarized using statistical analyses. The results demonstrate that the main types of contact among the particles are face-face, face-angle, face-edge, edge-edge, edge-angle and angle-angle contacts for particle sizes less than 0.2 mm. When the particle sizes are greater than 0.2 mm, the contacts are effectively summarized as face-face, face-angle, face-edge, edge-edge, edge-angle, angle-angle, sphere-sphere, sphere-face, sphere-edge and sphere-angle contacts. The differences in porosity among the original sample, reconstructed sample and regularized sample are closely related to the water-swelling and water-disintegrable characteristics of granite residual soil.

An attribute recognition model for safe thickness assessment between a concealed karst cave and a tunnel is established based on the attribute mathematic theory. The model can be applied to carrying out risk classification of the safe thickness between a concealed karst cave and a tunnel and to guarantee construction’s safety in tunnel engineering. Firstly, the assessment indicators and classification standard of safe thickness between a concealed karst cave and a tunnel are studied based on the perturbation method. Then some attribute measurement functions are constructed to compute the attribute measurement of each single index and synthetic attribute measurement. Finally, the identification and classification of risk assessment of safe thickness between a concealed karst cave and a tunnel are recognized by the confidence criterion. The results of two engineering application show that the evaluation results agree well with the site situations in construction. The results provide a good guidance for the tunnel construction.

Soft rock control is a big challenge in underground engineering. As for this problem, a high-strength support technique of confined concrete (CC) arches is proposed and studied in this paper. Based on full-scale mechanical test system of arch, research is made on the failure mechanism and mechanical properties of CC arch. Then, a mechanical calculation model of circular section is established for the arches with arbitrary section and unequal rigidity; a calculation formula is deduced for the internal force of the arch; an analysis is made on the influence of different factors on the internal force of the arch; and a calculation formula is got for the bearing capacity of CC arch through the strength criterion of bearing capacity. With numerical calculation and laboratory experiment, the ultimate bearing capacity and internal force distribution is analyzed for CC arches. The research results show that: 1) CC arch is 2.31 times higher in strength than the U-shaped steel arch and has better stability; 2) The key damage position of the arch is the two sides; 3) Theoretical analysis, numerical calculation and laboratory experiment have good consistency in the internal force distribution, bearing capacity, and deformation and failure modes of the arch. All of that verifies the correctness of the theoretical calculation. Based on the above results, a field experiment is carried out in Liangjia Mine. Compared with the U-shaped steel arch support, CC arch support is more effective in surrounding rock deformation control. The research results can provide a basis for the design of CC arch support in underground engineering.

Strainburst is one type of rockburst that generally occurs in deep tunnel. In this study, the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition, and two stress paths were designed, a commonly used stress path in true triaxial unloading rockburst tests and a new test path in which the intermediate principal stress was varied. During the tests, a high-speed camera was used to record the strainburst process, and an acoustic emission (AE) monitoring system was used to monitor the AE characteristics of failure. In these two stress paths, all the marble specimens exhibited strainbursts; however, when the intermediate principal stress was varied, the rockburst became more violent. The obtained results indicate that the intermediate principal stress has a significant effect on rockburst behavior of marble. Under a higher intermediate principal stress before the unloading, more elastic strain energy was accumulated in the specimen, and the cumulative AE energy was higher in the rockburst-induced failure, i.e., more elastic strain energy was released during the failure. Therefore, more violent failure was observed: more rock fragments with a higher mass and larger size were ejected outward.

The cost and safety of geotechnical engineering are highly depending on the accuracy of soil shear strength parameters. There are three methods often used to estimate soil shear strength parameters, i.e., moment method, 3-sigma rule and linear regression method. In this study, the accuracy of these three methods is compared. Traditional linear regression method (LRM) can only offer the mean of shear strength parameters. Some engineers misuse the standard error of shear strength indexes as the standard deviations. Such misuse may highly underestimate the uncertainty and induce high risk to the geotechnical design. A modified LRM is proposed to determine both the mean and variance of shear strength parameters. The moment method, three-sigma rule and LRM are used to analyze the tri-axial test data in Xiaolangdi Hydraulic Project and three numerical shear strength tests. The results demonstrate that: 1) The modified LRM can offer the most accurate estimation to shear strength parameters; 2) A dimensionless formula is much preferred in LRM rather than a dimensional formula. The stress ratio formula is much better than stress relation in the shear strength parameter analysis. The proposed method is applicable to shear strength parameter analysis for tri-axial test data, direct shear test and the un-drained shear strength test of stratified clay.

Airborne electromagnetic transient method enjoys the advantages of high-efficiency and the high resolution of electromagnetic anomalies, especially suitable for mining detection around goaf areas and deep exploration of minerals. In this paper, we calculated the full-wave airborne transient electromagnetic data, according to the result of numerical research, the advantage of switch-off time response in electromagnetic detection was proofed via experiments. Firstly, based on the full-wave airborne transient electromagnetic system developed by Jilin University (JLU-ATEM^I), we proposed a method to compute the full-waveform electromagnetic (EM) data of 3D model using the FDTD approach and convolution algorithm, and verify the calculation by the response of homogenous half-space. Then, through comparison of switch-off-time response and off-time response, we studied the effect of ramp time on anomaly detection. Finally, we arranged two experimental electromagnetic detection, the results indicated that the switch-off-time response can reveal the shallow target more effectively, and the full-waveform airborne electromagnetic system is an effective technique for shallow target detection.