Search

The long length, light weight, low frequency, flexible joint and link of large space manipulators impact dynamic stability and position accuracy seriously. In this paper, dynamical model of space flexible manipulators system is build base on Lagrange method. With three DOF manipulators as the research object, the impact of flexible link, joint stiffness and clearance on the system frequency and end position accuracy of manipulator is simulated and analyzed. The results indicate that the flexible joint lead to low frequency vibration and flexible link lead to high frequency vibration. Low frequency vibration is the dominant impact of end position accuracy, Flexible joint have greater impact on the dynamic characteristics of system than that of flexible link.

The force of ship is one of the main loads which High-Piled Wharf bears, the assignation of transverse component on each bent is the precondition of the calculation which simplified the wharf structure into plane bent. The taking value of transverse component on bent influences a lot on the result of structure calculation. Nowadays, the design of High-Piled Wharf uses the value from the distribution coefficient in the Design and Construction Code of High –Piled Wharf. The results show that the distribution coefficient taken in the code is under the precondition that considering the beam is rigid; the relative stiffness of beam and pile can influence this distribution coefficient. Considering the flexibility of the beam, the distribution coefficient of the horizontal concentrated force on transverse bents will change.

The recovery of polyvinyl alcohol (PVA) by flocculation method is investigated. The sodium polyphosphate is used as flocculating agent. The sodium sulfate produced by the relation between sodium hydroxide and sulfuric acid is used as salting-out agent. The sodium carbonate is used as coagulating agent. The optimal component ratio of flocculating agent, salting-out agent, coagulating agent is obtained by orthogonal experiment. The absorbency of PVA solution is selected as a reference index. PVA content was determined with spectrophotometry. The structure of recovered PVA is analyzed by infrared spectrum. The results show that the PVA recovery rate is as high as 96.5%.Keywords: flocculation method; PVA; sodium polyphosphate; orthogonal experiment

Carbon nanotubes (CNTs) were dispersed in aqueous solution with the inorganic compounds (H3O40PW12and H3BO3) by ultrasonic agitation. The dependency relationship between the inorganic solution concentration and CNTs dispersity was investigated by spectrophotometry. The results show that H3O40PW12and H3BO3can promote CNTs dispersion in aqueous solution. CNTs disperse very well in the appropriate concentration. The optimal concentration of H3O40PW12solution is 2mg/mL, and the optimal concentration of H3BO3solution is 4mg/mL. CNTs static stability in H3BO3solution is better than that in H3O40PW12. CNTs can still keep good dispersity in H3O40PW12solution under high speed centrifugation. The strong adsorption effect between CNTs surface and inorganic compound induces the dispersive stability of CNTs in aqueous solution.

Carbon nanotubes (CNTs) treated with an alkali solution were used to toughen epoxy resin (EP) by in-situ polymerization.The effects of different CNTs contents on the impact strength of EP were discussed. The morphology of impact section was investigated too.The results indicated that a certain amount of hydroxy groups were introduced on the surface of CNTs.The impact strength of EP is greatly enhanced with the increase of CNTs/EP weight ratio, and exhibited a maximum when ratio was 0.5.The toughness of CNTs/EP composites was remarkably improved.SEM showed that the fracture pattern of CNTs/EP composites was changed from brittle fracture to ductile fracture.

The modification of CaCO3powder was studied by the composite modifier in n-butanol and water solution. Aluminate coupling agent (ACA) and stearic acid (SA) were added as the composite modifier. The characters of modified CaCO3were investigated by the contact angles and infrared spectroscopy (IR). It was found that the contact angles/water of modified CaCO3powder increased with the increase of SA/ACA weight ratio, and showed a maximum when ratio was 0.8:1. The contact angles/water of modified CaCO3powder obtained in optimum conditions was 136.5°. The results indicated that the surface character of CaCO3powder exhibited hydrophobic properties. When adding the active CaCO3into PE (the weight ratio of CaCO3/PE about (20:100), the mechanical properties of PE were remarkably improved.

In order to study comparatively the effect of different rotor structure on variable speed constant frequency generation. The simulation performance comparisons between ALA reluctance rotor and cage rotor generator are presented in this paper by MATLAB software. It is indicated that ALA reluctance rotor and cage rotor exhibits fine variable speed constant frequency generation, however, the voltage harmonic of reluctance rotor generator is more than that of cage rotor generator.

In order to reach the object of test requirements of non-automatic weighing instruments, an automatic measurement method on weighing instruments is proposed, and a disseminating system is developed. The system includes automatic loading and unloading function without impact and adhesion. Therefore type evaluation tests of weighing instruments with the maximum capacity from 50 kg to 3000 kg such as indication error test, repeatability test, tare test, static temperature test and Damp heat test can be finished automatically by the system. The system can solve the problem that type evaluation test of weighing instruments with the maximum capacity above 50 kg is not performed by means of personnel. The experimental results show relative uncertainty of the system is not more than 5×10-6.

According to the measurement principle of magnetic parameter of weight, the influence of reading stability for measuring magnetism of weight is analyzed, and the key influence of reading stability is presented in the measurement process. The magnetism of weight is measured by the magnetic susceptometer with capacity of 5.1g and resolution of 0.1 mg. At the same time the change of environmental vibration at the laboratory and the fluctuating of ambient magnetic field are measured respectively. The experimental results show the fluctuating of ambient magnetic field that is the key influence parameter of weight magnetism measurement.

Risk matrix is applied to evaluate seismic risk on mountainous bridge. In this article, a continuous bridge is used as example to analyze the seismic risk of key position under a usual earthquake. Related control method is proposed to provide technical support for bridge seismic design and operation maintenance.