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The cone-beam oral CT requires high transmission accuracy, and harmonic reducers with smooth operation, high precision efficiency and safety factor are mostly used. Its flexspline is prone to failure due to periodic deformation under alternating load when rotating. The tooth profile of the flexspline is designed, modeled by SolidWorks, and imported into the Ansys Workbench for the static analysis, modal analysis, and transient dynamic analysis. The results show that the flexural strain is mainly located at the long and short axes of the wave generator, and the axial strain decreases gradually along the cylinder. The maximum stress is located at the contact between the wave generator and the flexspline, and the maximum stress is located at the connection between the tooth root and the cylinder during the transient dynamic analysis. At the same time, the stress and strain of the flexspline are also affected by tooth width, barrel length and barrel thickness.

Purpose: As the mining depth decreases, the reserves of ore in Daye iron mine gradually decrease. The effective way to solve the problems of large engineering quantity and high investment in deep mining development is to carry out the combination mining of the -- 450 m and -- 540 m levels. The feasibility and safety of high-level combination mining by filling method need to be explored and studied. To ensure the safety and efficiency of high-stage combination mining in Daye iron mine, based on engineering geological conditions and rock mass quality classification results, a study on optimization of structural parameters of high-stage combination mining in Daye iron mine was carried out. Method: On the basis of using the calculation method of the maximum unsupported span of the stope based on Q system rock mass classification and the introduction of ore and rock quality indexes, the maximum allowable safety span value of the stope can be calculated after analyzing the mining safety requirements and section size of each roadway of the mine and reasonably determining the corresponding stope structure parameters. In view of the impact of high-stage combination mining disturbance on the overlying rock formation, FLAC3D simulation software was used to conduct numerical simulation research on three schemes with stope heights of 105 m, 120 m, and 135 m. The displacement change values and stress distribution patterns of the stope roof and floor under different mining schemes were obtained. Result: When the stage height does not exceed 120 m, the maximum displacement occurs in the middle of the roof and floor plates and the deformation is small, resulting in less plastic damage areas, which can ensure safe mining of the mine. When the stope height reaches 135 m, tensile stress appears on both sides of the cement tailing backfill, and the displacement of the filling on both sides of the stope is large, exceeding the stope stability. Conclusion: The results show that; l)Combined with the Calculation of Maximum Unsupported Span of Stopes for Q System Rock Mass Classification method and comprehensively considering the influence of factors such as rock mass integrity, joint characteristics, groundwater, and ground stress, the limit span of high-stage combination mining in Daye iron mine is determined to be 20 m. 2) Based on the FLAC3D numerical simulation software, a comparative analysis of the stress field, displacement field, and plastic zone before and after one-step mining and two-step mining of the three stope stage heights was conducted, and it was determined that the stope height should not exceed 120 m. Significance; The research results are expected to provide a basis for the optimization of reasonable stope structure parameters for safe high-stage combination mining of Daye iron mine, and provide a reference for the design of stope structure parameters for high-stage mining of similar mines at home and abroad. [ABSTRACT FROM AUTHOR]

Paste filling technology represents the development direction of efficient, safe and green mining. However, due to the special requirements for the site, equipment, materials, time, safety and environmental protection, it is difficult to carry out the experimental teaching. Virtual simulation experiment has the characteristics of any time, safety and environmental protection, vividness, interactivity and immersion, which can partially replace the paste filling real experiment, enrich the experimental teaching content and fully inspire students' enthusiasm and initiative. In combination with the construction process of paste filling virtual simulation experimental teaching project of University of Science and Technology Beijing, this paper summarizes the significance of the project construction, technical route, construction content selection, resource construction mode, operation and maintenance mode, promotion and application, and explores upon the new direction, new ideas and new ways of teaching reform in traditional industries, which can provide reference for the construction of similar projects. [ABSTRACT FROM AUTHOR]

Porous stainless steel fiber materials with porosities ranging from 64.3% to 89.3% were prepared by sintering using 316L stainless steel fiber green felts with fiber diameters of 8 and 20 µm. The quasi-static compressive property of porous stainless steel fiber materials was tested using the INSTRON machine and the stress-strain curves were obtained using the Vic-3D non-contact strain tester. The deformation process was recorded using the high speed vidicon. Effects of the porosity, the fiber diameter, the thickness on the elastic modulus and the energy absorption capacity of porous stainless steel materials were studied systematically. Results show that the quasi-static compressive stress-strain curve of porous stainless steel fiber materials exhibits three unobvious regions, i.e., the elastic deformation stage, the strengthing stage with weak deformation and the strengthing stage with strong deformation. Furthermore, the elastic modulus and the energy absorption capacity increase constantly as the porosity of porous materials decreases. When the porosity of porous materials is 64.3%, the elastic modulus and the energy absorption capacity are 542 MPa and 27.7 MJ/m³, respectively. [ABSTRACT FROM AUTHOR]

Objective: To investigate the early change of brain-derived neurotrophic factor (BDNF) in denervated red and white muscles and the regeneration of nerves innervating the muscles and to discuss the effect of the target organs on regeneration of the injured nerves., Methods: Forty Wistar rats were divided into 5 groups. The sciatic nerves in 4 groups were sheared to make the models of the denervated muscles and the other one as control group. The amount of BDNF in muscles was measured with immunohistochemistry 1 day, 3 days, 7 days and 14 days after injury. The models of the regeneration of the nerves were made in another 15 rats whose sciatic nerves were disconnected with forceps. The nerve conduction velocity and electromyogram were tested with neuroelectrophysiology 7 days and 14 days after injury., Results: The expression of BDNF in soleus increased significantly on the 1st day, the 3rd day and the 7th day (P<0.01); the expression in gastrocnemius was lower, but there was no significant difference (P>0.05) on the 1st day, the 3rd day, the 7th day and the 14th day when compared with control group. After 14 days of injury in the nerves innervating GAS and SOL, the nerve conduction velocities and the amplitudes of wave M recovered to (36.60+/-7.40)% and (19.9+/-6.4)% of normal value, and (42.50+/-3.50)% and (13.7+/-4.0)% of normal value respectively; there were no significant differences between the two muscles (P>0.05)., Conclusion: There is difference in BDNF amount between the denervated red and white muscles, but the recovery of the two kinds of the motor nerves is similar, and the neurotrophism of denervated muscles was determined by all kinds of neurotrophic factors.