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The shortcomings of long period, high cost and slow response in making ceramic core by using investment casting method were overcome by using stereolithography and gel casting, which is of great significance for the rapid manufacturing of the single crystal blades with complex structure. The evolution rule of high temperature strength and shrinkage of silica based ceramic core was studied. The addition amount of nano zirconia power and aluminum powder and sintering time were explored. The micro morphology of the sample was characterized by field emission scanning electron microscope, and the high temperature strength of the sample was measured by three-point bending method. The results show that: when the mass fraction of nano zirconia power is 2.16%, the mass fraction of aluminum powder is 9.8% and the sintering time is 3.9 h, the maximum high temperature strength value of silicon oxide-based ceramic core reaches 14.3 MPa. The value of high temperature strength meets the needs of directional solidification casting of single crystal blade. There are no obvious cracks on the surface of the prepared ceramic core, the structure is complete and the molding quality is good.

The operating environment is polluted so seriously by shearer-generated dust that the shearer operators are one of most susceptible workers of coal pneumoconiosis in the mechanized coal mining workface of underground coal mines. In this work, we take 2214 mechanized coal mining workface of Liujialiang Coalmine in Xuangang Coal and Power Company Limited of Jinneng Holding Equipment Manufacturing Group as an example, and study the migration law of shearer-generated dust by numerical simulation. The results indicate that the falling height of the dust produced by the front cutting drum is more than that by the back one of the dual drum coal mining machine. The influence of equipment layout and strong turbulent air flow on the migration of coal dust produced by the front cutting drum is so great that they are quickly transported horizontally to the working area of the shearer operators, especially pathogenic dust below 5 μm, which is an important factor that causes the shearer operators to suffer from pneumoconiosis easily. The numerical simulation results are consistent with the field measurement of workface 2214.

The manufacturing technique of the top coal caving in coal mining of the upper and lower gateway in the working face is mainly along the coal seam bottom plate excavation. On the basis of the tunneling equipment used in the comprehensive tunneling face, our mine has developed the supporting technology and equipment of temporary support for rapid tunneling of top coal, that is, temporary support for rapid tunneling of top coal. Its purpose is to expand the area of temporary roof support, to realize the timely support of the new exposed roof cut by the roadheader, facilitate the parallel operation of various processes, protect the safety of personnel and equipment in the working space, shorten the operation time of permanent support, improve the efficiency of tunneling support work, accelerate the tunneling face tunneling speed. In order to ensure the safety of the workers in the tunneling face, the temporary support for rapid tunneling of top coal manufactured by SolidWorks software is checked and analyzed, which proves that the newly developed temporary support for rapid tunneling of top coal is safe and reliable.

C17H23N3O5, monoclinic, P21/n (No. 14), a = 12.8132(12) Å, b = 21.4531(19) Å, c = 15.3438(14) Å, β = 114.308(2)°, V = 3843.8(6) Å3, Z = 8, Rgt(F) = 0.0652, wRref(F2) = 0.2297, T = 296(2) K.

The issue of high dust concentration and the difficulty of head-on collection were investigated in this study. The theory of gas-solid two-phase flow was used to conduct numerical simulations on the air flow and dust concentration of the inside intake and the outside pressing particle collector using the FLUENT 6.3.26 software. The best optimization scheme was obtained by analyzing the simulation results of the air flow and dust concentration. Results indicated that when the diameter of the external cavity was 700 or 900 mm, the working surface of the working environment was not effectively improved. In comparison, when the diameter of the external cavity was optimized to 800 mm, most of the dust was trapped in the working face, and the working environment was significantly improved.

Manual measuring method for mine roadway section is time-consuming and laborious with big error, and existing measuring instruments of roadway section are poor in measuring speed and cannot realize real-time monitoring by upper computer. A design scheme of instantaneous monitoring system of mine roadway section was proposed based on PLC and ZigBee network. PLC of the system outputs two high-speed pulse sequences at 6 400 bit/s to control stepper motor to rotate and drive pulsed laser rangefinder to range respectively. High-speed counters of HC0, HC1 count two pulse sequences respectively. Step angle of the stepper motor is 0.45°. After laser rangefinder rotates 360°, the PLC calculates perimeter and area of roadway section and sends the results to upper computer through ZigBee network for real-time display. The experimental results show that the system updates to display perimeter and area of roadway section every 10 seconds. Relative error of perimeter measuring is no more than 0.5%, and the one of area measuring is no more than 0.9%.

In view of status of serious exterior ventilation leakage of auxiliary inclined air returning shaft used for staff and material transportation in Fengchishan Coal Mine, wind meter direct measuring method was used to test mine exterior ventilation leakage of selected test points, winch rope access window of explosion-proof ventilation door was determined as main ventilation leakage source according to change of exterior ventilation leakage rate. In view of problem that original closed method of winch rope access window easily led to ventilation leakage by use of rubber pad to fix on explosion-proof ventilation door, a reform scheme by use of movable baffle to close the window was proposed. The test results show that exterior ventilation leakage rate is reduced from 15.5% to 6.5% and negative pressure of ventilator is reduced by 318 Pa after reform.

C26H31N5O7, monoclinic, P21/n (no. 14), a = 7.0353(5) Å, b = 15.1943(8) Å, c = 24.8536(13) Å, β = 92.314(4)°, V = 2654.6(3) Å3, Z = 4, Rgt(F) = 0.0535, wRref(F2) = 0.1615, T = 296(2) K.