Worm grinding has been applied to manufacture gears to pursue high accuracy and fine surface finish. When the worm used to grind face gears is manufactured with multi-axis computer numerical control (CNC) machining, the machining accuracy is usually improved by increasing the number of tool paths with more time cost. Differently, this work proposes a generated method to improve the efficiency by dressing the worm surface with only one path, and a closed-loop manufacturing process is applied to ensure the machining accuracy. According to an advanced geometric analysis, the worm surface is practically approximated as a swept surface generated by a planar curve. Meanwhile, this curve is applied as the profile of a dressing wheel, which is used to dress the worm surface. The practical machining is carried out in a CNC machine tool, which was originally used to grind helical gears. Finally, a closed-loop manufacturing process including machining, measurement, and modification is proposed to compensate the machining errors. The proposed method is validated with simulations and practical experiments.

Graphene under high temperature was prepared and loaded on Ni foam. Then, cobalt tetroxide precursor was grown on Ni foam in situ by the hydrothermal method. Finally, the sample was burned at high temperature to obtain Co₃O₄+graphene@Ni. The hydrothermal method used in this paper is easy to operate, with low-risk factors and environmental protection. The prepared Co₃O₄+graphene@Ni electrode exhibits superior electrochemical performance than Co₃O₄@Ni electrode. At a current density of 1 A/g, the specific capacitance of the Co₃O₄+graphene@Ni electrode calculated by a charge-discharge test is 935 F/g, which is much larger than that of Co₃O₄@Ni electrode of 340 F/g.

The separation of Al from the silicon-rich diasporic bauxite is of great significance in alumina production. Herein, we proposed a low-temperature ammonium sulfate roasting-water leaching process to extract aluminum from silicon-rich diasporic bauxite. Parameters including roasting temperature, dosage of ammonium sulfate, roasting time, and particle size of ore were investigated. Under the condition of roasting temperature of 400 °C, roasting time of 5 h, ammonium sulfate dosage of 2.5 times of the theoretical value and ore particle size of 80–96 µm, more than 98% leaching rate of aluminum was obtained. The phase transformation and mechanism during the roasting process were revealed by using X-ray diffraction, thermogravimetric analysis, differential thermal analysis, and scanning electron microscope methods. The diaspore and kaolinite phases in the silicon-rich diasporic bauxite could react with ammonium sulfate to form corresponding sulfates (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃. The proposed technology could provide an effective method for the direct and separation of aluminum from silicon-rich diasporic bauxite.

High-temperature Ni-based alloys are widely used in the aerospace field due to their excellent properties, but the shortcomings of brittle fracture at the grain boundaries and poor plasticity at room temperature also limit their development to a certain extent. Researchers found that there are γ′ precipitation phases similar to Ni₃Al in Pt-Al based alloys. In this paper, the CASTEP code of Materials Studio software package is used to simulate the thermal and mechanical properties of γ′-Pt₃Al phase and γ′-Ni₃Al phase. By comparing the performance characteristics of the electronic structure, mechanical properties and point defect structure of the two, it is found that the stability, elastic deformation resistance and high temperature creep resistance of the γ′-Pt₃Al phase are better than those of the γ′-Ni₃Al phase. This will provide theoretical guidance for promoting the development of Pt-Al-based high-temperature materials.

The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering. At elevated temperatures, oxidation of the surfaces has an effective role in the fatigue strength and ductility of the alloys. In the present work, the effect of prior cyclic oxidation on the high temperature low cycle fatigue (HTLCF) properties of nickel-based superalloy Rene®80 has been assessed in the uncoated state and in the Pt-aluminide (Pt-Al) coated condition at 930 °C. To apply cyclic oxidation, simulation of engine thermal exposure was carried out by exposing coated and uncoated fatigue specimens in the burner rig (120 cycles at 1100°C). The cyclic oxidation procedure led to a changing in the coating microstructure from the dual-phase (ξ-PtAl₂ + β-(Ni, Pt) Al) to single phase (β-(Ni, Pt)Al). Results of HTLCF tests showed an improvement in the HTLCF life around 11.5% in the unexposed coated specimen (pre-cyclic oxidation) as compared to unexposed bare specimen, while this rise for exposed coated specimen (post-cyclic oxidation) was only 5%. Although a mixed mode fracture morphology (ductile and brittle) was observed on the fracture surfaces of failed specimens, the wider regions of brittle fracture belonged to exposed coated/uncoated ones.

The Al-Cu wheel adopting the new Al alloy was prepared by the liquid-die forging, and the mechanical properties, composition distribution, microstructure and fracture behavior were investigated. The results showed that serious Cu segregation was found in the wheel specimen; the microstructure of the Al-Cu wheel was comprised of the casting microstructure and a small amount of the deformed microstructure; the best heat treatment and water quenching system were found to solution treated at (530±5) °C for 4 h followed by (535±5) °C for 24 h and aging treated at (155±5) °C for 4 h; the fracture morphologies of the samples heated under T6 and T5-1 heat treatment showed flat, tough nest, and poor plastic characteristics; the fracture morphologies of the samples heated under T4 heat treatment exhibited complete resilience, but no residual metallographic characteristic; the sample treated under T4 protocol had the best elongation; the fracture failure was mainly due to the formation of the CuAl₂(θ) phases; and the fracture mechanism of the Al-Cu wheel was intergranular fracture.

Serving as gas diffusion layers (GDLs), the thermal conductivity of carbon paper (CP) plays a significant role in the heat transfer management in fuel cells. In the present study, the effect of graphitization degree of CP on its through-plane thermal conductivity and in-plane thermal conductivity is investigated. The relationship between heat treatment temperatures (1800, 2000, 2200, 2400 and 2500 °C) and graphitization degree is also investigated by SEM, XRD and Raman measurements. A model for CP under different graphitization degree is suggested considering the thermal conductivity difference of carbon fiber and matrix carbon. The experimental and simulation results are compared. The results show that the graphitization degree has a significant impact on the through-plane thermal conductivity and in-plane thermal conductivity.

This paper examines the effect of equalizing ignition delay in a compression ignition engine. Two sets of tests were conducted, i.e. a set of constant injection timing tests with start of fuel injection at 10° crank angle degree (CAD) before top dead center (BTDC) and a set of constant ignition timing tests while also keeping the 10° CAD BTDC injection and adding ignition improver (2-ethylhexylnitrate-, 2-EHN) to the fuel mixtures. Soot particles were characterized using DMS-500 instrument in terms of mass, size, and number. The experimental results showed that adding 2-EHN to the model fuel blends reduced the soot surface area, soot mass concentration and soot mean size. Replacing 20 vol% of a C₇-heptane with 20 vol% methyl-decanoate (an oxygenated C₁₁ molecule) did not affect the ignition delay or rate of fuel air premixing, the peak in-cylinder pressure or heat release rates. Toluene addition (0–22.5 vol%) to heptane increased the mean size of the soot particles generated by only 3% while also resulted in a slight increase in the peak cylinder pressure and peak heat release rates. Blending toluene and methyl-decanoate into heptane without adding 2-EHN increased the premix phase fraction by at least 13%. However, by adding 2-EHN (4×10⁻⁴−1.5×10⁻³), the premixed phase fraction decreased by at least 11%.

Fine particle flotation has been one of the main problems in many mineral processing plants. The bubble-particle collision rate is very low for fine particles, which reduces flotation efficiency. Also, the existence of slimes is, generally, detrimental to the flotation process, affecting the selectivity and the quality of the concentrates. Besides, it causes an increase in reagents consumption. Hence, in most of processing plants, some of these particles are transmitted to the tailing ponds to reduce the effects of these problems and increase the selectivity of the process. Esfordi phosphate plant in Iran loses more than 30% of its capacity as particles with d₈₀ finer than 30 µm. These fine particles with 15.9% P₂O₅ content are transferred to tailing dam. Processing of fine particles is very important for phosphate industry from economic and environmental aspects. This study addressed the processing of fine tailings (slimes) from a phosphate ore concentrator via flotation, despite the traditional view that ultrafine particles do not float. Phosphate flotation performances in the presence and absence of nanobubbles (NBs) in both mechanical and column cells were compared according to the metallurgical results of the process. NBs (generated by hydrodynamic cavitation) have interesting and exclusive properties such as high stability, durability and high surface area per volume, leading to increase of their utilization in mining-metallurgy and environmental areas. The results of this study revealed that, in the absence of NBs, a concentrate containing 26.9% P₂O₅ with a recovery of 29.13% was obtained using mechanical cells in comparison to 31.6% P₂O₅ with a recovery of 32.74% obtained using column flotation. In the presence of NBs, the recoveries of the concentrate of the mechanical and column flotation increased to 40.49% and 41.26% with 28.47% and 30.43% P₂O₅ contents, respectively. Comparative study showed that the column flotation was almost more efficient for processing the phosphate ore in the presence of the NBs, and had thicker froth layer compared to the mechanical flotation.

This study investigated the effect of repeated blasting on the stability of surrounding rock during the construction of a tunnel or city underground engineering. The split Hopkinson pressure bar (SHPB) was used to carry out cyclic impact tests on granite samples, each having a circular hole, under different axial pressures, and the cumulative specific energy was proposed to characterize the damage characteristics of the rock during the cyclic impact. The mechanical properties and the energy absorbed by the granite samples under cyclic impact loads were analyzed. The results showed that under different axial pressures, the reflected waveform from the samples was characterized by “double-peak” phenomenon, which gradually changed to “single-peak” with the increase in damage value. The dynamic peak stress of the sample first increased and then decreased with an increase in impact times. The damage value criterion established based on the energy dissipation could well characterize the relationship between the damage and the number of impacts, which showed a slow increase, steady increase, and high-speed increase, and the damage value depended mainly on the last impact. Under the action of different axial pressures, all the failure modes of the samples were axial splitting failures. As the strain rate increased, with an increase in the dimension of the block, the sizes of the rock fragments decreased, and the fragmentation became more severe.

The remanufacturing system is remolding the manufacturing industry by bringing scrapped products back to such a condition that reintegrated performance is just as good as new. The remanufacturing environment is featured by a far deeper level of uncertainty than new manufacturing, such as probabilistic routing files, and highly variable processing time. The stochastic disturbances result in the production bottlenecks, which constrain the productivity of the job shop. The uncertainties in the remanufacturing process cause the bottlenecks to shift when the workshop is processing. Considering this outstanding problem, many researchers try to optimize the production process to mitigate dynamic bottlenecks toward a balanced state. This paper proposes a data-driven method to predict bottlenecks in the remanufacturing system with multi-variant uncertainties. Firstly, discrete event simulation technology is applied to establish a simulation model of the remanufacturing production line and calculate the bottleneck index to identify bottlenecks. Secondly, a data-driven method, auto-regressive moving average (ARMA) model is employed to predict the bottlenecks in the system based on real-time data captured by the Arena software. Finally, the proposed prediction method is verified on real data from the automobile engine remanufacturing production line.

Several antennas based on cylindrical array and uniform hexagonal array are designed and fabricated on flexible substrate-Teflon. To validate the designed prototypes, the antennas are fabricated and their performance is analyzed. The highlight scheme is to improve the signal performance and electromagnetic field distribution by appropriately changing the parameters of the antennas array, signal frequencies, and steering angles. The proposed antennas array is capable of applying shaping radiation band technique to generate tunable power and radiation domain. The distribution of the field, and the bit-error-rate transmigration coefficient characteristics are measured. The results show that the proposed scheme can achieve better performance by searching the optimal parameters of antenna array.

A novel spiral non-circular bevel gear that could be applied to variable-speed driving in intersecting axes was proposed by combining the design principles of non-circular bevel gears and the manufacturing principles of face-milling spiral bevel gears. Unlike straight non-circular bevel gears, spiral non-circular bevel gears have numerous advantages, such as a high contact ratio, high intensity, good dynamic performance, and an adjustable contact region. In addition, while manufacturing straight non-circular bevel gears is difficult, spiral non-circular bevel gears can be efficiently and precisely fabricated with a 6-axis bevel gear cutting machine. First, the generating principles of spiral non-circular bevel gears were introduced. Next, a mathematical model, including a generating tooth profile, tooth spiral, pressure angle, and generated tooth profile for this gear type was established. Then the precision of the model was verified by a tooth contact analysis using FEA, and the contact patterns and stress distributions of the spiral non-circular bevel gears were investigated.

The operation variables, including feed rate of ore slurry, caustic solution and live steams in the double-stream alumina digestion process, determine the product quality, process costs and the environment pollution. Previously, they were set by the technical workers according to the offline analysis results and an empirical formula, which leads to unstable process indices and high consumption frequently. So, a multi-objective optimization model is built to maintain the balance between resource consumptions and process indices by taking technical indices and energy efficiency as objectives, where the key technical indices are predicted based on the digestion kinetics of diaspore. A multi-objective state transition algorithm (MOSTA) is improved to solve the problem, in which a self-adaptive strategy is applied to dynamically adjust the operator factors of the MOSTA and dynamic infeasible threshold is used to handle constraints to enhance searching efficiency and ability of the algorithm. Then a rule based strategy is designed to make the final decision from the Pareto frontiers. The method is integrated into an optimal control system for the industrial digestion process and tested in the actual production. Results show that the proposed method can achieve the technical target while reducing the energy consumption.

Different from the stable injection mode of conventional hydraulic fracturing, unstable fluid-injection can bring significant dynamic effect by using variable injection flow rate, which is beneficial to improve the fracturing effect. Obviously, the propagation process of fracturing fluid along the pipe string is crucial. In this paper, the fluid transient dynamics model in the pipe string was established, considering the boundary conditions of variable injection flow rate and reservoir seepage, and the unsteady friction was also taken into account. The above model was solved by characteristics and finite difference method respectively. Furthermore, the influences of geological parameters and fluid-injection schemes on fluctuating pressure were also analyzed. The results show that unstable fluid-injection can cause noticeable fluctuation of fracturing fluid in the pipe string. Simultaneously, there is attenuation during the propagation of pressure fluctuation. The variation frequency of unstable fluid-injection and well depth have significant effects on pressure fluctuation amplitude at the bottom of the well. This research is conducive to understanding the mechanism of unstable fluid-injection hydraulic fracturing and providing guidance for the design of fluid-injection scheme.

Nonlinear model predictive controllers (NMPC) can predict the future behavior of the under-controlled system using a nonlinear predictive model. Here, an array of hyper chaotic diagonal recurrent neural network (HCDRNN) was proposed for modeling and predicting the behavior of the under-controller nonlinear system in a moving forward window. In order to improve the convergence of the parameters of the HCDRNN to improve system’s modeling, the extent of chaos is adjusted using a logistic map in the hidden layer. A novel NMPC based on the HCDRNN array (HCDRNN-NMPC) was proposed that the control signal with the help of an improved gradient descent method was obtained. The controller was used to control a continuous stirred tank reactor (CSTR) with hard-nonlinearities and input constraints, in the presence of uncertainties including external disturbance. The results of the simulations show the superior performance of the proposed method in trajectory tracking and disturbance rejection. Parameter convergence and neglectable prediction error of the neural network (NN), guaranteed stability and high tracking performance are the most significant advantages of the proposed scheme.

Discrete manufacturing workshops are confronted with problems of processing diverse products and strict realtime requirements for data service calculation and manufacturing equipment, which makes it difficult to provide realtime feedback and compensation. In this study, a high-availability, high-performance, and high-concurrency digital twin reference model was constructed to satisfy a large number of manufacturing requirements. A multiterminal real-time interaction model and information aging classification rules for virtual and physical models were established. Moreover, a multiterminal virtual interaction model was proposed, and a generalized distributed computing service digital twinning system was developed. This digital twin system was considered a machine tool box processing line as an actual case. Consequently, a full closed-loop manufacturing process digital twin platform for physical request service, real-time response, and quality information feedback from iterations, which provides case guidance for subsequent factory digital twin systems, was realized. The proposed system can satisfy the requirements of multidevice big data computing services in modern manufacturing plants, as well as multiplatform, low-latency, and high-fidelity information visualization requirements for managers. Thus, this system is expected to play an important role in information factories.

The Ice, Cloud and Land Elevation Satellite-2 (ICESat-2), a new spaceborne light detection and ranging (LiDAR) system, was successfully launched on September 15, 2018. The ICESat-2 data increase the types of spaceborne LiDAR data archive and provide new control point data for large-scale topographic mapping and geodetic surveying. However, the accuracy of the ATL08 terrain estimates has not been fully evaluated on a large scale and in complex terrain conditions. This article aims to quantitatively assess the accuracy of ICESat-2 ATL08 terrain estimates. Firstly, the ICESat-2 ATL08 terrain estimates were compared with the high-precision airborne LiDAR digital terrain model (DTM), and impacts of acquisition time, vegetation cover type, terrain slope, and season change on the terrain estimation accuracy were analyzed. We get the following conclusions from the analysis: 1) the mean and RMSE of the terrain estimates of day acquisitions are 0.22 m and 0.59 m higher than that of night acquisitions; 2) the accuracy of the ATL08 terrain estimates acquired in vegetated areas is lower than those in non-vegetated areas; 3) the accuracy of the ATL08 terrain estimates is inversely proportional to the slope, and the elevation error increases significantly when the terrain slope is larger than 30°; 4) in the non-vegetation covered area, the accuracy of the ATL08 terrain estimates of summer and winter acquisitions has no obvious discrepancy, but in vegetated area, the accuracy of winter acquisitions is significantly better than that of summer acquisitions. This research provides references for the selection and application of ICESat-2 data.

Sheet metal forming, as a typical energy-intensive process, consumes massive energy. Due to the significant difference between sheet metal forming and machining, manufacturers still lack an effective method to monitor and analyze the energy efficiency in the sheet metal forming workshop. To this end, an energy efficiency monitoring and analysis (EEMA) method, which is supported by Internet of Things (IoT), is proposed. The characteristics in a forming workshop are first analyzed, and then the architecture of the method is expatiated-detailedly. Energy efficiency indicators at machine level, process level, and workshop level are defined, respectively. Finally, a sheet metal forming workshop for the deformation of panels of forklift was investigated to validate the effectiveness and benefits of the proposed method. With the application of the IoT-enabled method, various energy-saving decisions can be made by the management of the enterprises for energy efficiency improvement and energy consumption reduction (EEIECR) in the sheet metal forming workshop.

The main objective of this study is to investigate the effects of the nanoclay mixed with recycled polyester fiber on the mechanical behavior of soil as a new stabilizer material. To meet this objective, a series of drained direct shear and compaction tests were performed on unreinforced and reinforced soil specimens with three different combinations of the fiber-soil ratios ranging between 0.1% and 0.5%, as well as three different combinations of nanoclay-soil ratios ranging between 0.5% and 1.5% of the soil dry weight. Results indicated that composition of the nanoclay-recycled polyester fiber with the soil improved the friction angle (Φ) by 41% and cohesion (c) by 174%. The soil particles stick together through viscose gel produced by nanoclay. In addition, the rough and wavy surface of the fibers creates a bond and friction between the soil particles and prevents the movement of soil particles, and as a result, the soil strength is increased.

Following the assumptions proposed by MESRI and ROKHSAR, the one-dimensional nonlinear consolidation problem of soil under constant loading is studied by introducing continuous drainage boundary. The numerical solution is derived by using finite difference method and its correctness is assessed by comparing with existing analytical and numerical solutions. Based on the present solution, the effects of interface parameters, stress ratios (i.e., final effective stress over initial effective stress, N_σ) and the ratio c_c/c_k of compression index to permeability index on the consolidation behavior of soil are studied in detail. The results show that, the characteristics of one-dimensional nonlinear consolidation of soil are not only related to c_c/c_k and N_σ, but also related to boundary conditions. In the engineering practice, the soil drainage rate of consolidation process can be designed by adjusting the values of interface parameters.

The time-dependent rheological behaviors of alkali-activated cement (AAC) are expected to be precisely controlled, in order to meet the requirements of modern engineering practices. In this paper, the effects of activator, including the Na₂O concentration and SiO₂/Na₂O (S/N) molar ratio, on the rheological behavior of alkali-activated slag-fly ash pastes were investigated. The small amplitude oscillatory shear (SAOS) and shear test were used to evaluate the structural build-up and flowability of pastes. Besides, zeta potential measurement, calorimetric test and thermogravimetric analysis (TGA) were carried out to reveal the physico-chemical mechanisms behind the rheological evolution of fresh pastes. It was found that high Na₂O concentration and low S/N molar ratio improved the flowability and structural build-up rate of paste. Moreover, the structural build-up of alkali-activated slag-fly ash pastes consists of two stages, which is controlled by the dissolution of solid reactants and formation of C-(A)-S-H gels, respectively.

In this study, innovative ellipsoid pellet with craters on its surface was designed, and the direct reduction process was compared with ellipsoid (without craters) and sphere pellets. In addition, furnace temperature and uneven heat flux density effects on the pellet direct reduction process were also studied. The results show that ellipsoid pellet is better than that of spherical pellet on metallization ratio. However, under the condition of non-uniform heat flow, the ellipsoid pellet final metallization rate and zinc removal rate were lower. Although the heat transfer effect of ellipsoid pellet with craters was not improved significantly, the metallization rate and zinc removal rate were found improved, which will have a cumulative effect on the pellets direct reduction process in rotary hearth furnace. Under varying furnace temperature conditions, the pellet temperature was higher than that of the constant furnace temperature. After 1200 s, pellet Fe concentration increased to 123.6%, metallization rate and zinc removal rate increased to 113.7% and 102.2%, respectively. These results can provide references for the carbon-containing pellet design used in rotary hearth furnace.

Excessive vibrations inside buildings in the Lihu New Village caused by the Shenzhen Metro Line 2 underground railway were investigated by conducting analyses of the tunnel, the track irregularities, the stiffness of the fastening system, and the vibrations of the track system and the building at different speeds. A numerical simulation based on the dynamic coupling theory of the vehicle-track system was used to verify the experimental results. Suitable countermeasures were investigated. The results show that rail corrugation is the primary reason for the excessive vibration, and an increase in the stiffness of the vertical fastening system is the secondary reason. The solution was to eliminate the rail corrugation using rail grinding and decrease the vertical stiffness by changing the fastening system. The results of this study provide references for solving vibration problems caused by rail lines.

Because of the limitations of electric vehicle (EV) battery technology and relevant supporting facilities, there is a great risk of breakdown of EVs during driving. The resulting driver “range anxiety” greatly affects the travel quality of EVs. These limitations should be overcome to promote the use of EVs. In this study, a method for travel path planning considering EV power supply was developed. First, based on real-time road conditions, a dynamic energy model of EVs was established considering the driving energy and accessory energy. Second, a multi-objective travel path planning model of EVs was constructed considering the power supply, taking the distance, time, energy, and charging cost as the optimization objectives. Finally, taking the actual traffic network of 15 km×15 km area in a city as the research object, the model was simulated and verified in MATLAB based on Dijkstra shortest path algorithm. The simulation results show that compared with the traditional route planning method, the total distance in the proposed optimal route planning method increased by 1.18%, but the energy consumption, charging cost, and driving time decreased by 11.62%, 41.26% and 11.00%, respectively, thus effectively reducing the travel cost of EVs and improving the driving quality of EVs.

The roundabouts are widely used in China, some of which have central islands as scenic spots. The crosswalks connecting to the central islands, normally full of pedestrians, have negative impact on roundabout capability and pedestrian safety. Therefore, this study proposes a fuzzy cellular automata (FCA) model to explore the safety and efficiency impacts of pedestrian-vehicle conflicts at a two-lane roundabout. To reason the decision-making process of individual drivers before crosswalks, membership functions in the fuzzy inference system were calibrated with field data conducted in Changsha, China. Using specific indicators of efficiency and safety performance, it was shown that circulating vehicles can move smoothly in low traffic flow, but the roundabout system is prone to the traffic congestion if traffic flow reaches to a certain level. Also, the high yielding rate of drivers has a negative impact on the traffic efficiency but can improve pedestrian safety. Furthermore, a pedestrian restriction measure was deduced for the roundabout crosswalk from the FCA model and national guideline of setting traffic lights.