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In response to the control problems of large-deformation roadways in close-distance coal seams, taking a typical roadway under irregular goafs and residual coal pillar in deep close-distance coal seams as the background, the characteristics of mine pressure and key difficulties in surrounding rock control of roadway are explored and an improvement strategy for controlling surrounding rock is proposed. The stress expression in roadway floor under the influence of residual coal pillar is derived by theoretical calculation. The peak lines of deviatoric stress and vertical stress in roadway after the mining of the upper coal seam are obtained by numerical simulation. The roadway is divided into two key zones: ordinary zone and disturbance zone by residual coal pillar, and the disturbance range of roadway below residual coal pillar is determined to be 44.60 m. It reveals the differential, asymmetric, and non-uniform distortion and failure laws of roadway at different positions under irregular goafs and residual coal pillar. The differential control technology named asymmetric support in ordinary zone of roadway and combined support and drilling pressure relief in disturbance zone below residual coal pillar is proposed. The feasibility of differential pressure relief and control technology has been verified through on-site engineering test, which ensures the safety and stability of roadway and provides technical references for surrounding rock control in similar deep and complex roadways. [ABSTRACT FROM AUTHOR]

• Topology optimization for diffusion–reaction process in porous media is conducted. • The lattice Boltzmann method and the level-set method are coupled. • Delicately designed hierarchical porous structure are obtained. • Total reaction rate and material utilization ratio are evaluated. • Topology optimized structures overwhelm random hierarchical porous structure. Hierarchical porous media possess both high reactive sites and low transport resistance, yet the limit of the total reaction rate is not clear. In the present study, topology optimization (TO) of three-dimensional porous structures where diffusion–reaction processes occur is conducted by the lattice Boltzmann method and the level-set method to optimize the material distributions and to obtain the highest total reaction rate. Hierarchical porous structures are generated, and more mesoscopic pores are incorporated as the process gradually becomes diffusion-limited. The total reaction rate and utilization ratio of the microscopic materials are significantly improved in the TO structures. Compared with spherical structures, the TO results of spherical shell structures can significantly improve the material utilization ratio at the cost of slightly reduced total reaction rate. Finally, the TO structures are compared with random hierarchical structure, and remarkable increase of the total reaction rate is achieved. [ABSTRACT FROM AUTHOR]

In response to the shortcomings of the small support scope of single anchor cable and failure to fully utilize the joint anchoring for surrounding rock, this study summarizes the classification of basic support forms for coal mine roadway surrounding rock and clarifies the main composition and mechanism of anchor cable beam-truss structure. A mechanical model of roadway roof beam under the conditions of no support, single anchor cable support, and anchor cable beam-truss structure support at both ends of the roadway is constructed, and the force and maximum bending moment of roadway roof beam under different support types are compared and analyzed. The study clarifies the bending moment reduction rate of anchor cable beam-truss structure relative to unsupported and single anchor cable support and combines numerical simulation to analyze the response laws of anchor cable beam-truss to prestress distribution and stress shell in roadway surrounding rock. Based on the on-site engineering application of a typical large-deformation mining roadway in a deep coal mine, the important role of anchor cable beam-truss structure in ensuring the safety and stability of surrounding rock in deep high-stress and intense-mining large-deformation roadway is revealed, providing technical references for surrounding rock control of similar conditions in deep roadways. [ABSTRACT FROM AUTHOR]

• 3D multi-scale topology optimization of natural convection is studied. • Different microstructures of truss type and TPMS type are considered. • Optimized porous heat sinks better than conventional fins are obtained. • Heat dissipation performance of optimized designs is verified by FEM. • Effects of cell geometry, cell porosity and volume fraction are studied. This work presents a novel multi-scale topology optimization (TO) method for designing the three-dimensional porous heat sink to enhance the natural convection heat transfer. The pore-scale lattice Boltzmann model is applied to predict the effective transport properties while the level-set-based TO is performed at the representative elementary volume (REV)-scale. Six predetermined unit cells of distinct two types are considered, and the pore-scale study shows that the truss-type cells have higher permeability while lower effective thermal conductivity compared with the TMPS-type cells. The REV-scale TO generates the optimized designs when Grashof number (Gr) ranges from 2.4 × 102 to 1.2 × 105, which can enhance the heat transfer by 37.7 %∼49.1 % compared with the reference designs, and their performance is validated a posteriori with the relative error lower than 3 %. Parametric study finds that the optimized porous heat sinks made up of Primitive cell perform the best at all Gr values due to the higher effective thermal conductivity. Either decreasing the underlying porosity or increasing the filling volume of the porous material brings a better heat transfer performance, while the former approach is more effective. This work provides useful guidance to the choice of the underlying microstructure and to the topological design of porous heat sink. [ABSTRACT FROM AUTHOR]

Plate forming is an essential procedure in shipbuilding, which will influence the dimensional accuracy and fabrication schedule. Due to the advantages of induction heating for plate forming such as precision controlling, high level of automation, an experimental investigation for plate forming with multiple linear induction heating was carried out at first. With advanced 25 kW induction heating equipment and additional water cooling system, thermal cycles of several examined points during plate forming with induction heating was measured, and the influence of moving speed of induction heating coil on highest temperature of examined points was also investigated. Applying different heating pattern, plate with 6 mm in thickness will buckle as saddle shape due to the multiple-line heating in longitudinal direction and its generated large enough compressive force. Moreover, thermal elastic plastic (TEP) FE and elastic FE computational approaches were proposed and employed. Predicted out-of-plane bending deformations both have good agreement with measurement. Elastic FE computation with bending moment caused by induction heating as input load has effective advantage and high accuracy comparing to conventional thermal elastic plastic FE computation. [ABSTRACT FROM AUTHOR]

Multicomponent Pt-based catalysts with tunable compositions and nanostructures have attracted great interest owing to their promises of better catalytic performances and lower cost. In this work, we report the formation of porous Pt-Ni-Cu coatings with a wide range of compositions, tunable structures and improved electrocatalytic performances. The spongy Pt-Ni-Cu coatings were prepared by dynamic hydrogen bubble templated electrodeposition in highly diluted solutions. The chemical compositions and structures of the deposits exhibited a strong dependence on the concentrations of PtCl 4 2−, Cu2+ and Ni2+ ions in plating solutions. The as-prepared Pt-Ni-Cu foams, which had a honeycomb network structure composed by metallic nanodendrites, displayed both high catalytic activity and good stability towards the electrooxidation of methanol in alkaline media. The simplicity of the method and the outstanding catalytic performances of the spongy alloys suggested applications in preparing multicomponent platinum-derivated nanocatalysts in one step. Image 1 • Porous Pt-Cu-Ni coatings with a wide composition range and tunable structures were formed. • Both compositions and structures of deposits are highly sensitive to the metal ion concentrations. • Electronic effects and atomic-step growth on the sample surface improve catalytic activity. [ABSTRACT FROM AUTHOR]