Background The adverse consequences of medial meniscus posterior root tears have become increasingly familiar to surgeons, and treatment strategies have become increasingly abundant. In this paper, the finite element gait analysis method was used to explore the differences in the biomechanical characteristics of the knee joint under different conditions. Methods Based on CT computed tomography and MR images, (I) an intact knee (IK) model with bone, cartilage, meniscus and main ligaments was established. Based on this model, the posterior root of the medial meniscus was resected, and (ii) the partial tear (PT) model, (iii) the entire radial tear (ERT) model, and (iv) the entire oblique tear (EOT) model were established according to the scope and degree of resection. Then, the (v) meniscus repair (MR) model and (vi) partial meniscectomy (PM) model were developed according to the operation method. The differences in stress, displacement and contact area among different models were evaluated under ISO gait loading conditions. Results Under gait loading, there was no significant difference in the maximum stress of the medial and lateral tibiofemoral joints among the six models. Compared with the medial tibiofemoral joint stress of the IK model, the stress of the PM model increased by 8.3%, while that of the MR model decreased by 18.9%; at the same time, the contact stress of the medial tibiofemoral joint of the ERT and EOT models increased by 17.9 and 25.3%, respectively. The displacement of the medial meniscus in the ERT and EOT models was significantly larger than that in the IK model (P < 0.05), and the tibial and femoral contact areas of these two models were lower than those of the IK model (P < 0.05). Conclusions The integrity of the posterior root of the medial meniscus plays an important role in maintaining normal tibial-femoral joint contact mechanics. Partial meniscectomy is not beneficial for improving the tibial-thigh contact situation. Meniscal repair has a positive effect on restoring the normal biomechanical properties of the medial meniscus.

Based on the triaxial test of coarse grained soil, using the discrete element method to simulate the biaxial test by using PFC2D as the discrete element method (DEM) tools, and generate particles by a gradation which is similar with that in laboratory. Through self-programming, depends on the macro-reaction in lab to find out the mesoscopic parameters and deformation characteristics of coarse grained soil, then calibrate the value of friction coefficient correspond to that in laboratory, and at last find out the shear bands. The results show that the value of sample volumetric increment ratio (VIR)dεv/dεis positive (shear shrinkage) at first and then negative (shear dilation) when confining stress is 300kPa, when the confining pressure is greater than 300kPa, samples have been on the shear shrinkage.

A new relay protection based on electronic communication is presented for the access of distributed generation. After distributed generation access to the system, distribution network power flow direction and short-circuit current level will change. This paper describes the effects of distributed generation on distributed network by building feeder system simplified PSCAD/ EMTDC model. According to the analysis, the new relay protection can improve the stability and reliability of distributed network.

As the high concrete faced rockfill dams construction, grain breakage gradually become the factors that influence the high dam construction which can not be ignored. This text based on the master of rockfill of shuibuya dam as the experimental material, getting and analyzing the particle breakage data under different confining pressure through the large-scale triaxial test, and the results show that the particle breakage index increases with the increase of confining pressures. The relationship between particle breakage index and confining pressure can be expressed by formula;Particle breakage increase leading to reduced internal friction angle and the shear strength of rockfill, and the author newly introduced two broken variable to describe the relationship which can be expressed by the formula between the particle breakage and internal friction angle, it has certain reference value for establishing constitutive model considering particle breakage.