The gob side entry retaining with high water material is often used in coal mines. To study the stress evolution characteristics of surrounding rock and asymmetric support control technology of gob side entry retaining with high water material, the evolution law of stress and deformation of surrounding rock in gob side entry retaining during working face mining is studied by theoretical analysis, numerical simulation and field measurement. According to the stress variation of overlying strata during the mining process of the working face, the mechanical models before and after the basic roof fracture were established respectively. The stress and deformation of the filling body and the roof on the side of the filling body are larger, and the stress and deformation of the solid coal and the roof on the side of solid coal are smaller. The maximum stress is at 3 m away from the roadway. The first weighting step distance is 40 m and the periodic weighting step distance is 30 m. Based on the stress and deformation characteristics of the roadway surrounding, the roadway surrounding support is divided into filling bodyside, solid coal side, and middle part of roadway roof. The asymmetric support technology of "filling body+ double row hydraulic prop+ I-beam+ high-strength pretension anchor cable+ high-strength bolt" is proposed. The field engineering practice shows that the surrounding rock control effect of asymmetric support technology with high water material is good., Qiyuan Shan, Yongli Liu, Tao Li and Zhupeng Jin., and Obsahuje bibliografii
Hypoxia training can improve endurance performance. However, the specific benefits mechanism of hypoxia training is controversial, and there are just a few studies on the peripheral adaptation to hypoxia training. The main objective of this study was to observe the effects of hypoxia training on cutaneous blood flow (CBF), hypoxia-inducible factor (HIF), nitric oxide (NO), and vascular endothelial growth factor (VEGF). Twenty rowers were divided into two groups for four weeks of training, either hypoxia training (Living High, Exercise High and Training Low, HHL) or normoxia training (NOM). We tested cutaneous microcirculation by laser Doppler flowmeter and blood serum parameters by ELISA. HHL group improved the VO2peak and power at blood lactic acid of 4 mmol/l (P4) significantly. The CBF and the concentration of moving blood cells (CMBC) in the forearm of individuals in the HHL group increased significantly at the first week. The HIF level of the individuals in the HHL group increased at the fourth week. The NO of HHL group increased significantly at the fourth week. In collusion, four weeks of HHL training resulted in increased forearm cutaneous blood flow and transcutaneous oxygen pressure. HHL increases rowers’ NO and VEGF, which may be the mechanism of increased blood flow. The increased of CBF seems to be related with improving performance.
Traditional depth-averaged morphodynamic models for turbidity currents usually focus on the propagation of currents after plunging. However, owing to the unsteady characteristic of the plunge point locations and the tough conditions of field measurement within the plunge zone in a reservoir, it is difficult in practice to directly provide upstream boundary conditions for these models. A one-dimensional (1D) morphodynamic model coupling open-channel flow and turbidity current in a reservoir was proposed to simulate the whole processes of turbidity current evolution, from formation and propagation to recession. The 1D governing equations adopted are applicable to open-channel flows and turbidity currents over a mobile bed with irregular cross-section geometry. The coupled solution is obtained by a two-step calculation mode which alternates the calculations of open-channel flow and turbidity current, and a plunge criterion is used to determine the location of the upstream boundary for the turbidity current, and to specify the corresponding boundary conditions. This calculation mode leads to consecutive predictions of the hydrodynamic and morphological factors, from the open-channel reach to the turbidity current reach. Turbidity current events in two laboratory experiments with different set-ups were used to test the capabilities of the proposed model, with the effect of free-surface gradient also being investigated. A field-scale application of the coupled model was conducted to simulate two turbidity current events occurring in the Sanmenxia Reservoir, and the method for calculating the limiting height of aspiration was adopted to estimate the outflow discharge after the turbidity currents arrived in front of the dam. The predicted plunge locations and arrival times at different cross-sections were in agreement with the measurements. Moreover, the calculated interface evolution processes and the sediment delivery ratios also agreed generally with the observed results. Therefore, the 1D morphodynamic model proposed herein can help to select the design capacity of the outlets, and optimize the procedure for sediment release in reservoirs.