Analysis of the Internal Characteristics of a De ector Jet Servo Valve

In current research on deflector jet servo valves, the receiver pressure estimated using traditional two-dimensional simulation and theoretical calculation is always lower than the experimental data; therefore, credible information about the flow field in the prestage part of the valve can hardly be obtained. To investigate this issue and understand the internal characteristics of the deflector jet valve, a realistic numerical model is constructed and a three-dimensional simulation carried out that displays a complex flow pattern in the deflector jet structure. Then six phases of the flow pattern are presented, and the defects of the two-dimensional simulation are revealed. Based on the simulation results, it is found that the jet in the deflector has a longer core area and the fluid near the shunt wedge cannot resist the impact of the high-speed fluid. Therefore, two assumptions about the flow distribution are presented by which to construct a more complete theoretical model. The receiver pressure and prestage pressure gain are significantly enhanced in the calculations. Finally, special experiments on the prestage of the servo valve are performed, and the pressure performance of the numerical simulation and the theoretical calculation agree well with the experimental data. Finally, the internal mechanism described by the theoretical and numerical models is verified. From this research,more accurate numerical and theoretical models are proposed by which to figure out the internal characteristics of the deflector jet valve.

Removal of lead from aqueous solution by hydroxyapatite/ manganese dioxide composite

A novel composite adsorbent, hydroxyapatite/ manganese dioxide （HAp/MnO2）, has been developed for the purpose of removing lead ions from aqueous solutions. The combination of HAp with MnO2 is meant to increase its adsorption capacity. Various factors that may affect the adsorption efficiency, including solution pH, coexistent substances such as humic acid and competing cations （Ca2＋, Mg2＋）, initial solute concentration, and the duration of the reaction, have been investigated. Using this composite adsorbent, solution pH and coexistent calcium or magnesium cations were found to have no significant influence on the removal of lead ions under the experi- mental conditions. The adsorption equilibrium was described well by the Langmuir isotherm model, and the calculated maximum adsorption capacity was 769 mg. gl. The sorption processes obeyed the pseudo-second-order kinetics model. The experimental results indicate that HAp/MnO2 composite may be an effective adsorbent for the removal of lead ions from aqueous solutions.

Adaptive sliding mode control of multi-agent relay tracking systems with disturbances

This paper studies the switching topologies and tracking agent replacements for a class of nonlinear multi-agent systems with external disturbances.In particular,it is assumed that a number of monitoring agents are randomly deployed in a two-dimensional space.The agents are committed to tracking any intrusion targets in this area.When one of the following agents exits tracking for some reasons,the agent closer to the target joins the tracking team to ensure the number of tracking agents does not change.In order to achieve the successful tracking of the target,this paper designs a sliding mode controller for the relay multi-agent system with tracking agent replacements.Furthermore,an adaptive law is proposed to estimate the upper bound of disturbance in the relay tracking process.Next,the stability of the overall system will be analysed by applying the multiple Lyapunov function method based on the average dwell time.Finally,the effectiveness of the tracking strategy is verified by numerical simulations.