Search

In order to solve the problems of comprehensive flexibility of robot arm, and expand the application field of service robot and improve the safety, a one-dimensional two-way flexible bending joint is developed by using the self-developed pneumatic artificial muscle. The relevant theoretical model is established and the relevant experimental analysis is carried out. The experimental results show that the bending joint can realize one-dimensional two-way bending motion and the bending angle of the joint can be controlled by adjusting the gas pressure; when the air pressure difference between the two sides of the leaf spring is 0.22Mpa, the maximum bending angle of the joint reaches 74.12 degrees; the forward and reverse bending of the joint are consistent, and the joint bending curve is similar to the arc.

The characteristics of fast electrons (e-) and heavy particles (N2+, N+, N2f, Nf) in the cathode dark space (CDS) of nitrogen dc glow discharge are simultaneously studied by Monte Carlo simulation. The calculated energy and angular distributions of these particles at different positions from the cathode provide a clear picture of their transport behaviours within the CDS. The density and mean energy of these particles indicate that the electrons and the atomic ions (N+) are the main high-energy species and the molecular ions (N2+) are the major ions in the CDS. It can be seen from the energy distributions of the bombarding particles at the cathode surface that the molecular ions and the fast atoms (Nf) are the main active species participating in the cathode nitride material synthesis process. The influence of the backscattering of the electrons from the negative glow to the CDS is also investigated. All the calculated results provide good information on the spatial characteristics of the particles considered in this paper and also their internal connections in the CDS of nitrogen dc glow discharge.

A cellular automaton model has been developed to simulate the austenitization process of ASTM A216 WCA cast steel during heating process. The dissolution of pearlite and the transformation of ferrite into austenite were simulated. The calculation domain was divided into square cells, which are characterized by certain attributes that represent the status of each cell: pearlite (P), ferrite (α), austenite (γ) or γ /α interface. The dissolution of pearlite was described by nucleation and growth of austenite. A mixed-mode model in multicomponent system was employed to calculate the growth velocity of the γ /α interface. According to Burke and Turnbull's theory, austenite grain coarsening induced by γ /γ grain boundary migration was simulated. To validate the model, dilatometric and quenching experiments were carried out. The dilatometric experiment was conducted using a Gleeble1500D with a sample 8 mm in diameter. The temperature of the sample was measured using thermocouples welded on the sample surface. In the quenching experiments, steel samples were heated to different temperatures then dropped into a water tank immediately, and the microstructure of the samples was examined to determine the fraction of the austenite. The simulated results were compared with the experimental results and the capability of the model for quantitatively predicting the microstructure evolution of the steel in heating process was assessed.

Manganese dioxide has attracted much attention owing to its distinctive properties. A facile method was developed to synthesis γ-MnO2 by the reaction of Na2S2O8 with Zn-bearing MnSO4, keeping the molar ratio of Mn to S as 1:2-4. The oxidation of Mn2+ increased from 62.3% to 99.9% with the increase of the final solution pH from 0.55 to 4.45. The needlelike γ-MnO2 particles with a length of 200-500 nm and a diameter of 10-30 nm were synthesized in the initial solution pH range of 3.5-4.0. γ-MnO2 particles with poor crystallinity and porous morphology were synthesized in the initial solution pH range of 6.0-6.5. The Zn2+ adsorption capacities of the γ-MnO2 formed at initial pH = 3.5 and pH = 6.0 were 131.8 mg.g−1 and 527.4 mg.g−1, respectively.