Aiming at the problem of skidding in the operation of a self-propelled high-stem crop sprayer due to uneven road surface and uneven distribution of soil cohesive force,This study proposed a four-wheel drive hydraulic ...Aiming at the problem of skidding in the operation of a self-propelled high-stem crop sprayer due to uneven road surface and uneven distribution of soil cohesive force,This study proposed a four-wheel drive hydraulic anti-skid control system based on RTM valve.Through theoretical analysis of control components such as the RTM valve and steering cylinder,the control model of the anti-skid drive system of the spray machine is established,and the simulation test is carried out in Matlab/Simulink.The simulation results show that the slip rate of the anti-skid drive system based on the PID control strategy is controlled below 0.05,and the RTM valve keeps the driving pressure of the system basically stable.In order to verify the reliability of the simulation results,the designed drive anti-skid control system was carried out on a spray machine for the field test.The experimental results show that the slip rate of the drive anti-skid system decreases from 86.7%to 1.25%when the anti-skid function is turned on,indicating that the designed drive anti-skid system has good anti-skid performance.展开更多
背景:程序性细胞死亡受体1(programmed death receptor-1,PD-1)在高糖环境下影响骨髓间充质干细胞成骨分化的作用机制尚不清楚。目的:探讨高糖环境中PD-1对大鼠骨髓间充质干细胞成骨分化的影响及其调控机制。方法:将大鼠骨髓间充质干细...背景:程序性细胞死亡受体1(programmed death receptor-1,PD-1)在高糖环境下影响骨髓间充质干细胞成骨分化的作用机制尚不清楚。目的:探讨高糖环境中PD-1对大鼠骨髓间充质干细胞成骨分化的影响及其调控机制。方法:将大鼠骨髓间充质干细胞随机分为正常糖组(5.6 mmol/L)、高糖组(30 mmol/L)、PD-1过表达组、PD-1过表达空载组、PD-1敲低组、PD-1敲低空载组、PI3K/AKT通路抑制剂组(PD-1敲低+5μmol/L LY294002)。通过在高糖培养基中培养大鼠骨髓间充质干细胞来模拟体外糖尿病环境,采用qRT-PCR检测大鼠骨髓间充质干细胞中PD-1及其配体PD-L1和成骨标志物Runx2、OSX的mRNA表达,采用碱性磷酸酶染色和茜素红S染色观察成骨分化能力,采用CCK-8检测细胞增殖情况,采用Western blot检测PD-1、PD-L1、p-PI3K、p-AKT的蛋白表达。结果与结论:①高糖组PD-1及PD-L1表达显著高于正常糖组,高糖组骨髓间充质干细胞的成骨分化能力较正常糖组显著下降;②敲低PD-1表达可以促进骨髓间充质干细胞的成骨分化、增加细胞增殖活性,同时激活PI3K/AKT通路;③加入PI3K/AKT通路抑制剂LY294002后,骨髓间充质干细胞成骨分化能力显著下降。结果表明:PD-1依赖于PI3K/AKT信号通路抑制高糖环境下大鼠骨髓间充质干细胞的成骨分化。展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2016YFD0200705)the Key Laboratory of Northwest Agricultural Equipment of the Ministry of Agriculture and Zhongnong Fengmao Plant Protection Machinery Co.,Ltd.
文摘Aiming at the problem of skidding in the operation of a self-propelled high-stem crop sprayer due to uneven road surface and uneven distribution of soil cohesive force,This study proposed a four-wheel drive hydraulic anti-skid control system based on RTM valve.Through theoretical analysis of control components such as the RTM valve and steering cylinder,the control model of the anti-skid drive system of the spray machine is established,and the simulation test is carried out in Matlab/Simulink.The simulation results show that the slip rate of the anti-skid drive system based on the PID control strategy is controlled below 0.05,and the RTM valve keeps the driving pressure of the system basically stable.In order to verify the reliability of the simulation results,the designed drive anti-skid control system was carried out on a spray machine for the field test.The experimental results show that the slip rate of the drive anti-skid system decreases from 86.7%to 1.25%when the anti-skid function is turned on,indicating that the designed drive anti-skid system has good anti-skid performance.
