Corrosion behaviors of P110 and N80 tubular steels in CO₂ gas phase and supercritical (S-CO₂) phase in a saturated water vapor environment were explored in corrosion weight loss experiments by SEM, EDS, XRD, XPS and cross-section analysis techniques. With the increase in CO₂ partial pressure, the average corrosion rate increased first and then decreased. The average corrosion rate reached the maximum value under the near-critical pressure. When CO₂ partial pressure further increased to be above the critical pressure, the average corrosion rate gradually decreased and local aggregation of molecules was weakened.

The apparent activation energy for deformation (Q) and strain rate sensitivity (m) of GH4586 superalloy are calculated and the variation trend is reasonably explained by the microstructure observations. Constitutive modelling of this superalloy is established and the processing maps at different strains are constructed. The results show that the Q value is in the range of 751.22–878.29 kJ/mol. At a temperature of 1060 °C, strain rate of 0.001 s⁻¹, and strain of 0.65, the m value of GH4586 superalloy reaches a maximum of 0.42. The optimal processing parameter of GH4586 superalloy is at a deformation temperature of 1050 °C and a strain rate of 0.001 s⁻¹. The domains of flow instability notably expand with increasing strain during high temperature deformation of GH4586 superalloy.

The article improves the process of dielectric barrier discharge (DBD) activated anode bonding. The treated surface was characterized by the hydrophilic surface test. The results showed that the hydrophilic angle was significantly reduced under nano-gap conditions and the optimal discharge voltage was 2 kV Then, the anodic bonding and dielectric barrier discharge activated bonding were performed in comparison experiments, and the bonding strength was characterized by tensile failure test. The results showed that the bonding strength was higher under the nano-gap dielectric barrier discharge. This process completed 110 °C ultra-low temperature anodic bonding and the bonding strength reached 2 MPa. Finally, the mechanism of promoting bonding after activation is also discussed.

Sodium-ion batteries are considered as a promising candidate for lithium-ion batteries due to abundant sodium resources and similar intercalation chemistry. Hard carbon derived from biomass with the virtue of abundance and renewability is a cost-effective anode material. Herein, hard carbon is derived from renewable bagasse through a simple two-step method combining mechanical ball milling with carbonization. The hard carbon electrodes exhibit superior electrochemical performance with a high reversible capacity of 315 mA-h/g. Furthermore, the initial capacity of the full cell, HC//NaMn_0.4Ni_0.4Ti_0.1Mg_0.1O₂, is 253 mA·h/g and its capacity retention rate is 77% after 80 cycles, which further verifies its practical application. The simple and low-cost preparation process, as well as excellent electrochemical properties, demonstrates that hard carbon derived from bagasse is a promising anode for sodium-ion batteries.

Laboratory-scale experiments were performed to investigate the deoxidation of H13 tool steel with CaF₂-MgO-Al₂O₃-CaO-SiO₂ slags at 1873 K. The calculation of thermodynamics and kinetics was also verified through the experimental results. The results show that [Si]-[O] reaction is the control reaction, and with the increase of basicity of slag, the limitation of deoxidation was decreased. The limitation of deoxidation is the lowest for the slag with basicity of 2.0. Under the conditions of the basicity of 2.0 and the content of CaF₂ more than 50%, the limitation of deoxidation is less than 10 × 10⁻⁶, and it does not depend on the contents of Al₂O₃ and CaF₂ in slags. The mass transport of oxygen in the metal phase is the rate-controlling step, and the slag composition has no effect on the equilibrium time of deoxidation. Based on this finding, the optimized slag composition is designed and it contains the following components: 51.5% CaF₂ 20.3% MgO, 16.2% Al₂O₃, 8.2% CaO and 3.8% SiO₂. In the case of the optimized deoxidizing slag, the total oxygen content in H13 steel can be reduced from 25 × 10⁻⁶ to 6 × 10⁻⁶.

A new process of AlN removal from secondary aluminum dross (SAD) by pyrometallurgical treatment with added cryolite was applied for solving the problem of recycling the secondary aluminum dross. The response surface methodology (RSM) was used to design experiments and optimize parameters. The results show that adding the appropriate amount of cryolite can effectively promote the oxidation of AlN in the SAD, and too much cryolite will reduce the promotion effect. The effects of roasting temperature and cryolite on the denitrification rate are the most significant (p < 0.0001) followed by holding time. Predicted values of the denitrification rate are found to be in good agreement with experimental values (R² = 0.9894 and

, which confirms the validity of the model employed. The optimum conditions of roasting temperature of 750 °C, holding time of 194 min, mass fraction of cryolite of 17.7% are obtained according to the quadratic model. Under these conditions, the maximum actual denitrification rate reaches 94.71% and the AlN content in the SAD is only 0.55 wt%. The unfired brick with compressive strength of 18.62 MPa (GB/T 2542-2012) was prepared based on the roasted SAD.

In order to analyze the lubricating characteristics at different meshing points in the cycloid pin wheel transmission process, the cycloid gear teeth were discretized, combined with the kinematic analysis of the cycloid pin gear transmission and the contact analysis of the gear teeth. The progressive mesh densification method (PMD) was used to numerically solve the film thickness. The influence of the design parameters and process parameters on the lubrication characteristics was analyzed. The elastohydrodynamic lubrication and mixed lubrication characteristics at different contact points were obtained. The optimal meshing area of the cycloid gear tooth was determined, and the film thickness ratio, contact load ratio, maximum contact pressure at different points, average film thickness and roughness after contact deformation were analyzed. The conclusion of this study provides effective guidance for the research on the modification of cycloid gear teeth.

In view of the axial force produced in the working process of double arc helical gear hydraulic pump, the theory of differential equation of curve and curved surface was utilized so that the calculation formula of axial force was obtained and the relationship between the axial force and structure parameters of gears was clarified. In order to balance the axial force, the pressure oil in the high pressure area was introduced into the end face of the plunger to press the plunger against the gear shaft, and the hydrostatic bearing whose type is plunger at the end of the shaft was designed. In order to verify the balance effect of axial force, the leakage owing to end clearance and volume efficiency of gear hydraulic pump before and after the balancing process was analyzed. This paper provides a new analysis idea and balance scheme for the axial force produced in the working process of the double arc helical gear hydraulic pump, which can reduce the leakage owing to end clearance caused by the axial force and improve the volume efficiency of the gear hydraulic pump.

A semi-analytical method to conduct vibro-acoustic analysis of a composite laminated elliptical shell immersed in air is proposed. A variational method and multi-segment technique are used to formulate the dynamic model. The sound radiation of the exterior fluid field is calculated by a spectral Kirchhoff-Helmholtz integral formulation. The variables containing displacements and sound pressure are expanded by the combination of Fourier series and Chebyshev orthogonal polynomials. The collocation points are introduced to construct an algebraic system of acoustic integral equations, where these points are distributed on the roots of Chebyshev polynomials, and the non-uniqueness solution of system is eliminated by a combined Helmholtz integral. Numerical examples for sound radiation problems of composite laminated elliptical shells are presented and individual contributions of the circumferential modes to the acoustical results of composite laminated elliptical shells are also given. The effects of geometric and material parameters on sound radiation of composite laminated elliptical shells are also investigated.

Failures due to high-cycle fatigue have led to a high cost in aerospace engineering over the past few decades. In this paper, the experimental results of the fatigue behavior of compressor blade specimen subjected to resonance and the effects of a damping hard coating on relieving the fatigue progress are presented. The crack initiation and propagation processes were observed under resonance of the first bending mode by using the resonant frequencies as the indicator. Significant nonlinear features were observed in the spectrum of the blade with a fatigue crack. The finite element model considering the breathing crack was established with nonlinear contact based on the crack localization and size, which was obtained by ultrasonic phased array technology. The simulation results of the vibration behavior of the cracked blade were obtained and consistent with the experimental results. A NiCrAlY coating was deposited on the blade, and increases in the fatigue life were observed under the same condition. The results of this paper can help to better understand the fatigue of a compressor blade subjected to resonance and provide a preference for the application of a damping hard coating on compressor blades.

Extremely hard and abrasive rocks pose great challenges to the past and ongoing TBM projects by increasing cutter wear and reducing penetration rates. A considerable amount of research has been conducted to improve the performance of TBMs in those challenging grounds by either improving the capacity of TBMs or developing assisting rock breakage methods. This paper first highlights the challenges of hard and abrasive rocks on TBM tunneling through case studies. It then presents the development of hard rock TBMs and reviews the technologies that can be used individually or as assistance to mechanical excavators to break hard rocks. Emphases are placed on technologies of high pressure waterjet, laser and microwave. The state of the art of field and laboratory research, problems and research directions of those technologies are discussed. The assisting methods are technically feasible; however, the main challenges of using those methods in the field are that the energy consumption can be over 10 times high and that the existing equipments have robustness problems. More research should be conducted to study the overall energy consumption using TBMs and the assisting methods. Pulsed waterjet, laser and microwave technologies should also be developed to make the assistance economically viable.

Large-scale electric vehicles (EVs) connected to the micro grid would cause many problems. In this paper, with the consideration of vehicle to grid (V2G), two charging and discharging load modes of EVs were constructed. One was the disorderly charging and discharging mode based on travel habits, and the other was the orderly charging and discharging mode based on time-of-use (TOU) price; Monte Carlo method was used to verify the case. The scheme of the capacity optimization of photovoltaic charging station under two different charging and discharging modes with V2G was proposed. The mathematical models of the objective function with the maximization of energy efficiency, the minimization of the investment and the operation cost of the charging system were established. The range of decision variables, constraints of the requirements of the power balance and the strategy of energy exchange were given. NSGA-II and NSGA-SA algorithm were used to verify the cases, respectively. In both algorithms, by comparing with the simulation results of the two different modes, it shows that the orderly charging and discharging mode with V2G is obviously better than the disorderly charging and discharging mode in the aspects of alleviating the pressure of power grid, reducing system investment and improving energy efficiency.

Destination prediction has attracted widespread attention because it can help vehicle-aid systems recommend related services in advance to improve user driving experience. However, the relevant research is mainly based on driving trajectory of vehicles to predict the destinations, which is challenging to achieve the early destination prediction. To this end, we propose a model of early destination prediction, DP-BPR, to predict the destinations by users’ travel time and locations. There are three challenges to accomplish the model: 1) the extremely sparse historical data make it challenge to predict destinations directly from raw historical data; 2) the destinations are related to not only departure points but also departure time so that both of them should be taken into consideration in prediction; 3) how to learn destination preferences from historical data. To deal with these challenges, we map sparse high-dimensional data to a dense low-dimensional space through embedding learning using deep neural networks. We learn the embeddings not only for users but also for locations and time under the supervision of historical data, and then use Bayesian personalized ranking (BPR) to learn to rank destinations. Experimental results on the Zebra dataset show the effectiveness of DP-BPR.

Due to global energy depletion, solar energy technology has been widely used in the world. The output power of the solar energy systems is affected by solar radiation. Accurate short-term forecasting of solar radiation can ensure the safety of photovoltaic grids and improve the utilization efficiency of the solar energy systems. In the study, a new decomposition-boosting model using artificial intelligence is proposed to realize the solar radiation multi-step prediction. The proposed model includes four parts: signal decomposition (EWT), neural network (NARX), Adaboost and ARIMA. Three real solar radiation datasets from Changde, China were used to validate the efficiency of the proposed model. To verify the robustness of the multi-step prediction model, this experiment compared nine models and made 1, 3, and 5 steps ahead predictions for the time series. It is verified that the proposed model has the best performance among all models.

Rockburst prediction is of vital significance to the design and construction of underground hard rock mines. A rockburst database consisting of 102 case histories, i.e., 1998–2011 period data from 14 hard rock mines was examined for rockburst prediction in burst-prone mines by three tree-based ensemble methods. The dataset was examined with six widely accepted indices which are: the maximum tangential stress around the excavation boundary (MTS), uniaxial compressive strength (UCS) and uniaxial tensile strength (UTS) of the intact rock, stress concentration factor (SCF), rock brittleness index (BI), and strain energy storage index (EEI). Two boosting (AdaBoost.M1, SAMME) and bagging algorithms with classification trees as baseline classifier on ability to learn rockburst were evaluated. The available dataset was randomly divided into training set (2/3 of whole datasets) and testing set (the remaining datasets). Repeated 10-fold cross validation (CV) was applied as the validation method for tuning the hyper-parameters. The margin analysis and the variable relative importance were employed to analyze some characteristics of the ensembles. According to 10-fold CV, the accuracy analysis of rockburst dataset demonstrated that the best prediction method for the potential of rockburst is bagging when compared to AdaBoost.M1, SAMME algorithms and empirical criteria methods.

In actual production, deep coal mine roadways are often under typical static-dynamic coupling stress (SDCS) conditions with high ground stress and strong dynamic disturbances. With the increasing number of disasters and accidents induced by SDCS conditions, the safe and efficient production of coal mines is seriously threatened. Therefore, it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS. In this paper, the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations, and the deformation and failure characteristics are obtained. According to the simulation results, the horizontal stress, vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock. Among these factors, the influence of the dynamic disturbance is the most substantial. Under the same stress conditions, the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor. The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses. The results indicate that for the roadway under high-stress conditions, the in-situ stress test must be strengthened first. After determining the magnitude of the in-situ stress, the location of the roadway should be reasonably arranged in the design to optimize the mining sequence. For roadways that are strongly disturbed by dynamic loads, rock supports (rebar/cable bolts, steel set etc.) that are capable of maintaining their effectiveness without failure after certain dynamic loads are required. The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS, and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

In this study, the micro-failure process and failure mechanism of a typical brittle rock under uniaxial compression are investigated via continuous real-time measurement of wave velocities. The experimental results indicate that the evolutions of wave velocities became progressively anisotropic under uniaxial loading due to the direction-dependent development of micro-damage. A wave velocity model considering the inner anisotropic crack evolution is proposed to accurately describe the variations of wave velocities during uniaxial compression testing. Based on which, the effective elastic parameters are inferred by a transverse isotropic constitutive model, and the evolutions of the crack density are inversed using a self-consistent damage model. It is found that the propagation of axial cracks dominates the failure process of brittle rock under uniaxial loading and oblique shear cracks develop with the appearance of macrocrack.

To research the anchoring effect of large deformation bolt, tensile and drawing models are established. Then, the evolution laws of drawing force, bolt axial force and interfacial shear stress are analyzed. Additionally, the influence of structure element position on the anchoring effect of large deformation bolt is discussed. At last, the energy-absorbing support mechanism is discussed. Results show that during the drawing process of normal bolt, drawing force, bolt axial force and interfacial shear stress all gradually increase as increasing the drawing displacement, but when the large deformation bolt enters the structural deformation stage, these three values will keep stable; when the structure element of large deformation bolt approaches the drawing end, the fluctuation range of drawing force decreases, the distributions of bolt axial force and interfacial shear stress of anchorage section are steady and the increasing rate of interfacial shear stress decreases, which are advantageous for keeping the stress stability of the anchorage body. During the working process of large deformation bolt, the strain of bolt body is small, the working resistance is stable and the distributions of bolt axial force and interfacial shear stress are steady. When a rock burst event occurs, the bolt and bonding interface cannot easily break, which weakens the dynamic disaster degree.

Excavation-induced microseismicity and rockburst occurrence in deep underground projects provide invaluable information that can be used to warn rockburst occurrence, facilitate rockburst mitigation procedures, and analyze the mechanisms responsible for their occurrence. Based on the deep parallel tunnels with the maximum depth of 1890 m created as part of the Neelum-Jhelum hydropower project in Pakistan, similarities and differences on excavation-induced microseismicity and rockburst occurrence between parallel tunnels with soft and hard alternant strata are studied. Results show that a large number of microseismic (MS) events occurred in each of the parallel tunnels during excavation. Rockbursts occurred most frequently in certain local sections of the two tunnels. Significant differences are found in the excavation-induced microseismicity (spatial distribution and number of MS events, distribution of MS energy, and pattern of microseismicity variation) and rockbursts characteristics (the number and the spatial distribution) between the parallel tunnels. Attempting to predict the microseismicity and rockburst intensities likely to be encountered in subsequent tunnel based on the activity encountered when the parallel tunnel was previously excavated will not be an easy or accurate procedure in deep tunnel projects involving complex lithological conditions.

The safety factor of roof under deep high stress is a quantitative index for evaluating roof stability. Based on the failure mode of surrounding rock of stope roof, the mechanics model of goaf roof is constructed, and the internal force of roof is deduced by the theory of hingeless arch. The calculation method of roof safety factor (K) under the environment of deep mining is proposed in view of compression failure and shear failure of roof. The calculation formulas of shear safety factor (K₁), compression safety factor (K₂) and comprehensive safety factor (K) of roof are given. The influence of stope span and roof thickness on roof stability is considered in this paper. The results show that when the roof thickness remains constant, the roof safety factor decreases with the increasing of the stope span; when the stope span remains constant, the roof safety factor increases with the increasing of the roof thickness. The deep mining example shows that when the stope span is 30 m and the roof thickness is 10 m, the roof comprehensive safety factor is 1.12, which indicates the roof is in a stable state.

To keep the tunnel face stable is very important for tunnel construction. In this paper, the tunnel face stability under the advanced pipe was analyzed using the Winkler foundation model and rigid limit equilibrium. The tunnel face deformation characteristics were also analyzed using the numerical simulation. The influence of parameters on the deflection of the pipe roof and the stability of the tunnel face were discussed. The results show that the tunnel face stability can be improved through increasing the pipe diameter, decreasing the initial displacement at the beginning of the pipe seat, and adopting the short round length and small excavation height. With the increase of tunnel burial depth, the safety factor of tunnel face stability first decreases, then increases, and then remains unchanged. The deformation at the center of the tunnel face is larger than the deformation at the surround sides and at the corner. The horizontal displacement varies little with the increasing of the pipe length. The horizontal displacement at the center of the tunnel face increases with the increase of the pipe ring spacing and the pipe longitudinal spacing. There is an optimum external angle.

In order to reveal the changing law of the mechanical response of asphalt pavements under the action of vehicle load and provide references for the design of durable pavements, three typical asphalt pavement structures with flexible base (S1), combined base (S2), and semi-rigid base (S3) were selected to perform field strain tests under static and dynamic load using the fiber Bragg grating optical sensing technology. The changing characteristics of the strain field along the horizontal and depth directions of pavements were analyzed. The results indicate that the most unfavorable asphalt pavement layers were the upper-middle surface layer and the lower base layer. In addition, the most unfavorable loading positions on the surface layer and the base layer were the center of wheel load and the gap center between two wheels, respectively. The most unfavorable layer of the surface layers gradually moved from the lower layer to the upper layer with the increase of base layer modulus. The power function relationships between structural layer strain and vehicle speed were revealed. The semi-rigid base asphalt pavement was the most durable pavement type, since its strain value was lower compared to those of the other structures.