Composite silicone rubber of high piezoresistance repeatability filled with nanoparticles

The ruthenium oxide nanoparticles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparticles in air, which were synthesized by using the thermal reduction in the polyol solution. The rutile structure of the ruthenium oxide was proved by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The oxide has good electron conductivity. The surface of the ruthenium oxide was modified by a vinyl silane coupling agent. The assembling of the silane to the oxide surface was proved by Infrared (IR) absorption spectroscopy. By mixing the nanoparticles with poly(methylvinylsiloxane) (PMVS) silicone rubber, a composite filled with dispersive conducting phase was fabricated. The temperature dependent conductivity shows that the electron transportation through composite is mainly dominated by tunneling. The measurement of piezoresistance shows that the composite at low strain has high piezoresistance repeatability. The 3D reconstruction images of the composite filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites. The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence.     

A physically-based integrated numerical model for flow,upland erosion,and contaminant transport in surface-subsurface systems

This paper presents a physically-based integrated hydrologic model that can simulate the rainfall-induced 2D surface water flow, 3D variably saturated subsurface flow, upland soil erosion and transport, and contaminant transport in the surface-subsurface system of a watershed. The model couples surface and subsurface flows based on the assumption of continuity conditions of pressure head and exchange flux at the ground, considering infiltration and evapotranspiration. The upland rill/interrill soil erosion and transport are simulated using a non-equilibrium transport model. Contaminant transport in the integrated surface and subsurface domains is simulated using advection-diffusion equations with mass changes due to sediment sorption and desorption and exchanges between two domains due to infiltration, diffusion, and bed change. The model requires no special treatments at the interface of upland areas and streams and is suitable for wetland areas and agricultural watersheds with shallow streams.     

Precision forming machine with rolling plate cross wedge rolling

Roller cross wedge rolling (CWR) machines have high rigidity, but sector dies are difficult to process. Plate CWR machines have low rigidity and need large floor space, but plate dies are easy to process. Neither roller CWR machine nor plate CWR machine can produce larger workpieces. Based on the above conclusions, this paper presents the mechanical principle of the precision forming machine with rolling plate CWR. Then, its design principle and machine construction are presented. There are a top press roller above the upper sliding plate and a bottom press roller under the lower sliding plate. The press rollers make rolling contact with the sliding plates. The plate dies are mounted on the upper and lower sliding plates, respectively. Furthermore, the axes of both press rollers and centerline of workpiece always keep in the identical vertical plane during forming process. These make the machine retain advantages of high rigidity for roller CWR machine and simpleness of manufacturing dies for plate CWR machine, and abandon defects of poor rigidity for plate CWR machine and difficulty of manufacturing dies for roller CWR machine. Moreover, the machine can produce larger workpieces.     

Effects of irrigation efficiency on chemical transport processes

Irrigation practices greatly affect sustainable agriculture development. In this study, we investigated the effects of irrigation efficiency on water flow and chemical transport in soils, which had significant impact on the environment. Field dye staining experiments were conducted at different soils with various irrigation amount. Image analysis was conducted to study the heterogeneous flow patterns and their relationships with the irrigation efficiency. Irrigation efficiency and its environmental effects were evaluated using various indictors, including application efficiency, deep percolation ratio, storage efficiency, and uniformity. Under the same irrigation condition, soil chemical distributions were more heterogeneous than soil water distributions. The distributions were mainly affected by soil texture, initial soil water content, and irrigation amount. Storage efficiency, irrigation uniformity, and deep percolation ratio increased with irrigation amount. Since the chemical distribution uniformity was lower than the water uniformity, the amount of chemical leaching increased sharply with decrease of irrigation uniformity, which resulted in high environmental risks of groundwater pollution.     

Earth pressure balance control for EPB shield

This paper mainly deals with the critical technology of earth pressure balance (EPB) control in shield tunneling. On the assumption that the conditioned soil in the working chamber of the shield is plasticized, a theoretical principle for EPB control is proposed. Dynamic equilibrium of intake volume and discharge volume generated by thrust and discharge is modeled theoretically to simulate the earth pressure variation during excavating. The thrust system and the screw conveyor system for earth pressure cont...     

Vertical shaking table tests on the structure with viscoelastic multi-dimensional earthquake isolation and mitigation devices

The viscoelastic multi-dimensional earthquake isolation and mitigation device is a new kind of passive control device, which can perform its "name-giving" task of earthquake isolation and earthquake mitigation simultaneously. In order to quantify its vertical earthquake isolation and mitigation effect on structures, firstly, shaking table tests on steel frame structures with and without the devices were carried out; secondly, analysis on dynamic characteristics and dynamic responses of the structures was al...     

Mathematical models of grinding manufacture and tooth contact analysis of spherical gears

The spherical gear is a gear-driven mechanism with two degrees of freedom (DOF), which can transfer spatial motion and power. Grinding machining of the spherical gear is performed with a plate grinding wheel by using generating method, and based on mathematical model of the plate grinding wheel, the mathematical model of the spherical gear is set up. And then, the meshing model of a spherical gear pair is developed and the tooth contact analysis (TCA) of the spherical gear pairs is performed. After that, th...     

Discrimination for ablative control mechanism in solid-propellant rocket nozzle

The ablation in solid-propellant rocket nozzle is a coupling process resulted by chemistry, heat and mass transfer. Based on the heat and mass transfer theory, the aero-thermo-dynamic, and thermo-chemical kinetics, the thermal-chemical ablation model is established. Simulations are completed on the heat flow field and chemical ablation in the nozzle with different concentrations, frequency factors and activation energy of H2. The calculation results show that the concentration and the activation energy of H...     

捕收剂在硫化矿物表面吸附机理的研究进展

综述了药剂与硫化矿表面吸附作用机理的理论研究,总结了现代表面测试技术在硫化矿表面吸附作用机理研究中的应用前景．表面测试技术在选矿中的应用,使矿物与药剂的吸附机理研究更加深入,也促进了浮选理论和工艺技术的持续发展和不断完善．     

基于改进PSO算法的自适应均衡算法

传统的自适应均衡算法存在收敛速度慢,稳定性差、均衡效果不理想等缺点,从而使自适应均衡器在高速光纤通信系统中的应用受到限制.具有梯度搜索因子的Grads-PSO算法,结合了传统数值优化方法在计算速度和计算精度上的优势,将梯度法引入粒子群算法中.在梯度搜索因子的指导下,PSO算法的运算过程显得更加有规则,从而提高了算法的收敛速度和运算精度.因此,本文提出将改进PSO算法用作自适应均衡器均衡算法.通过仿真实验表明,改进PSO算法具有收敛速度快,计算精度高的优点,将其作为自适应均衡器的控制算法可收到很好的均衡效果,优于传统的控制算法.