Teeter Bed Separators (TBS) are liquid–solid fluidized beds that are widely used in separation of coarse particles in coal mining industry. The coal particles settle in the self-generating medium bed resulting in separation according to density. Due to the existence of self-generating medium beds, it is difficult to study the sedimentation of particles in TBS through experiments and detection methods. In the present research, a model was built to investigate the bed expansion characteristics with water velocity based on the Euler–Euler approach, and to investigate the settling of foreign particles through bed based on the Euler–Lagrange approach in TBS. Results show that the separation of in TBS should be carried out at low water velocity under the condition of stable fluidized bed. Large particles have a high slip velocity, and they are easily flowing through the bed into the light product leading to a mismatch. The importance of self-generating bed on separation of particle with narrow size ranges are clarified. The model provides a way for investigating the separation of particles in a liquid–solid fluidized bed and provides suggestions for the selection of operation conditions in TBS application.
As a natural polymer, gelatin is increasingly being used as a substitute for animals or humans for the simulation and testing of surgical procedures. In the current study, the similarity verification was neglected and a 10 wt.% or 20 wt.% gelatin sample was used directly. To compare the mechanical similarities between gelatin and biological tissues, different concentrations of gelatin samples were subjected to tensile, compression, and indentation tests and compared with porcine liver tissue. The loading rate in the three tests fully considered the surgical application conditions; notably, a loading speed up to 12 mm/s was applied in the indentation testing, the tensile test was performed at a speed of 1 mm/s until fracture, and the compression tests were compressed at a rate of 0.16 mm/s and 1 mm/s. A comparison of the results shows that the mechanical behaviors of low-concentration gelatin samples involved in the study are similar to the mechanical behavior of porcine liver tissue. The results of the gelatin material were mathematically expressed by the Mooney-Rivlin model and the Prony series. The results show that the material properties of gelatin can mimic the range of mechanical characteristics of porcine liver, and gelatin can be used as a matrix to further improve the similarity between substitute materials and biological tissues.
Accurately mastering the power transmission characteristics of the cutting arm transmission shaft system is key to improving the reliability and working capacity of the cantilever roadheader. Based on the rigid–flexible coupling vibration characteristic modeling of the roadheader cutting arm, the vibration characteristics of different substructures in the transmission shaft system of the roadheader cutting arm were considered, the dynamic characteristic model was comprehensively constructed, and the numerical analysis was carried out with the parameters of the XTR260 tunnel hard rock roadheader to compare the vibration characteristics of the cutting head under different cutting conditions. The experiment was carried out by using an artificial concrete wall, and the measurement results verify the established dynamic model that lays the foundation for the dynamic design of a high-performance roadheader.
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