Research on the "shape-performance-control" integrated digital twin system for boom-type roadheaders.

The boom-type roadheader plays a crucial role in coal mining. However, conducting the real-time monitoring of the mechanical performance and comprehensive adaptive cutting in the dynamic cutting process are challenging. To address these issues, a digital twin system that integrates the elements of "shape, performance, and control" for roadheaders is presented in this paper. The system comprises three components: physical space, service space, and twin space. The service space forms the core of the entire system. Within this space, twin models and control models are created using numerical simulation, artificial intelligence and multi-source data fusion technology. These models serve the purpose of predicting the roadheader's mechanical performance and controlling the swing speed of the cutting arm. The physical space is built using technologies such as robot kinematics, electrical systems, hydraulic transmission, and other relevant techniques. This approach facilitates the transmission of multi-sensor data to twin models. The control model then manages the roadheader's function based on the output signals from the control model. The twin space is constructed utilizing physical rendering engines, databases, and 3D modelling tools. This space visualizes and stores the movement, performance, and control parameters of the roadheader. The results demonstrate that the average absolute error between the measured data from the test's three position strain gauges and the predicted data from the twin system is 10.38 MPa. Furthermore, the twin system achieves an average update interval of 0.34 s, allowing real-time stress monitoring of the structural components of the roadheader and preventing damage caused by overload. The proposed control model enables adaptive adjustment of the swing speed of the cutting arm in approximately 0.3 s. This improvement significantly enhances the adaptive cutting capabilities of roadheaders when dealing with complex coal and rock formations.

Research on the comparison of impact resistance characteristics between energy absorption and conventional hydraulic columns in fluid-solid coupling.

Rock burst disaster affects underground mining safety. The energy-absorbing hydraulic support for preventing tunnel impact has been implemented in rock burst mines. In order to compare the impact resistance characteristics of conventional columns and energy-absorbing columns, based on the derivation of energy theory, the CEL fluid-solid coupling simulation algorithm is used to simulate the process of static load 1000 kN superimposed impact load 1500 kN on φ180 mm type conventional column and energy-absorbing column. Combined with the static-dynamic combined test of the 6500 kN impact testing machine on the column, the accuracy and reliability of the CEL simulation column impact response are verified. The results showed that compared with conventional columns, the reaction force of energy-absorbing columns is reduced by 32.55%. The stress and expansion of the cylinder are significantly reduced. The acceleration of the mass movement has been reduced by 59.46%. The addition of the energy-absorbing device enhances the system's energy absorption by 33.46%, thereby reducing the energy absorption of the column itself to 23.58%. Additionally, the deformation of the energy-absorbing device increases the effective displacement by 239.45%. This also prolongs the impact duration, ensuring sufficient time for the safety valve to open, safeguarding the support from damage, and enhancing the overall integrity of the tunnel.

[Repairing of upper cicatricial ectropion with orbicularis oculi myocutaneous flap in construction of double eyelid].

OBJECTIVE: To investigate a method for upper cicatricial ectropion correction using a rotated orbicularis oculi myocutaneous flap in the unsatisfied pre-operative construction of double eyelid. METHODS: In construction of double eyelid, orbicularis oculi myocutaneous flap made by relaxed skin and orbicularis oculi was used to correct ectropion. RESULTS: From Feb. 2003 to Dec. 2005, the authors performed correction of ectropion for 13 patients. All of these patients were followed up, and the period ranged from 2 weeks to 6 months. All of these patients received good results except one. It was corrected again for the flattening of the pedicle 6 months later. CONCLUSIONS: Orbicularis oculi myocutaneous flap has a rich blood supply. The ratio of its length and width can be made to 6:1, and it can be transferred flexibly. In addition, the incision of the donor site is hidden in fold of double eyelid.