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Owing to low dry mass, high precision thrust control, simple structure and no pollutions, the nitrogen gas micro-propulsion systems can meet the demands of drag-free satellites where the payload follows a geodesic path through space only perturbed by gravity and not by non-gravitational forces. In this study, the nitrogen gas micro-propulsion system was modeled using AMESim software. Present onedimensional system model consisted of two nitrogen tanks, a latching valve, a pressure reducing valve and a piezoelectric proportional valve which driven by piezoelectric patches and integrated with a thruster. The nitrogen gaseous pressure in the tank and the buffer cavity of the proportional valve were set to 150 bar and approx. 2. 0 bar, respectively. The electromechanical coupling coefficient, elastic constants and relative permittivity of the piezoelectric patches were varied from 0. 518 to 0. 962, 1. 536e-l1 to 2. 834e – 11 and 3500 to 7500, respectively. The modelling results revealed that compared to elastic constants and relative permittivity, the electromechanical coupling coefficient had a most influence on the opening of valve and thrust force.

On the basis of the natural disaster system theory, this paper takes the danger of hazard inducing factors, stability of hazard inducing environment and vulnerability of hazard bearing body into consideration. Ten indexes including precipitation, typhoon, elevation, slope, river buffer, runoff, road, population, GDP and agricultural land are selected in this paper to evaluate the flood risk in Dongjiang River Basin, with the application of GIS technology and the Principal Component Analysis (PCA) method. The results show that the highest risk zones and higher risk zones occupy above 25% of the basin area while the lowest risk zones and lower risk zones make up about 45%. Flood disaster mainly concentrates in such regions as Shenzhen, Huizhou, Heyuan city; the results are objective and reasonable, compared with actual conditions. In sum, the PCA method is strict and convenient, which provides a reasonable, reliable way for flood risk assessment.

An automatic, convenient method combined flow injection technique for determining organic phosphorus pesticide in environment water was developed based on the inhibition effects of organic phosphorus pesticide to plant-esterase. The optimized determining conditions were acquired, and the analytical characteristics of this method were studied. The linear ranges of dichlorvos' standard curves was 0.008 ∼ 4mg/L. The linear equation of dichlorvos was U(mV) = −4874.4 C (mg/L) + 110313. The correlation coefficient of dichlorvos was 0.9984. The detection limit (S/N= 3) was 0.02mg/L for dichlorvos. The relative standard deviation (RSD) of dichlorvos was 1.04% (n=6). The recoveries ranged from 95% to 105%. The analysis result was good.

Automatic profiled fiber identification is of very significance to textiles quality control and performance design. In this paper, we present a facile sequential clustering algorithm used for profiled fiber identification. This clustering algorithm is based on dissimilarity measures between feature vectors. One of its advantages is that the final result is independent on the order in which the vectors are presented to the algorithm. Our profiled fiber identification system employs a feature extracting technique that uses the shape information residing in the boundary curve of profiled fiber cross-sections. The experimental results show that the defined shape descriptor and the classification method can effectively identify solid profiled fibers that differ in their cross-sectional shapes.

This paper presents a comprehensive study on the effects of the caudal fin shape on the biomimetic propulsion performance of a harmonically heaving and pitching caudal fin. A propulsion system was designed and a series of hydrodynamic experiments for three caudal fin shapes (the whale caudal fin, the dolphin caudal fin, and the tuna caudal fin) were performed. Then numerical simulations based on RANS equations were taken. Both computational and experimental results indicate that the tuna caudal fin produces the highest efficiency. However the mean thrust coefficient of the tuna caudal fin is the smallest. It is found that although the mean thrust coefficient for the tuna caudal fin is not large, input power of the tuna caudal fin is also quite small.

In this paper, the hydrodynamic performances of unsteady flapping foil were studied by panel method based on potential flow theory. The flapping foil had a coupling motion of rolling and pitching. The calculation process of panel method was realized by the FORTRAN procedure. The calculation results of average thrust coefficient by the procedure accordance well with the MIT experiment data. Then the FLUENT software was applied and the results also compared well with the experiment data. The results of other hydrodynamic coefficients by panel method compared well with those by the FLUENT software. So the procedure for panel method was considered available. The thrust coefficient, the lift coefficient and the propulsion efficiency of the unsteady flapping foil were obtained. Then the effects of some parameters including the incoming velocity, the flapping amplitude, the phase difference and the oscillating frequency to the hydrodynamic performances were investigated.

The characteristic of path planning for underwater vehicle is large planning area and sparse obstacles, effect of sea current. A new path planning approach in this paper is presented. In the method, trunk binary tree is used for environment modeling and search space generating so that planning area can be ignored. The heuristic evaluation function is designed by colligating path length, Ocean current and obstacles' cost. A* heuristic evaluation arithmetic is used for getting the path by the least cost. Particle swarm optimization (PSO) in path planning is used for largely reducing disadvantage effect of ocean current and energy cost more. Simulation results prove the effectiveness of this approach which fulfills the demand of path planning for underwater vehicle.

In nature a lot of fishes realize to suspend itself in water, to go forward and to move back up by the pectoral fin moving complexly. So that it is significant theoretically and valuable for practical application to investigate the propulsive principle and hydrodynamic performance of pectoral fin and find the method utilizing the pectoral fin to maneuver the underwater bio-robot agilely. The pectoral fin in propulsive system was composed of two servomotors to obtain various demanded feathering lead-lag coupling motions within the system limitation. The motion was sinusoidal in the experiment. The parameters included phase difference, oscillating frequency, oscillating amplitudes and angular bias. The hydrodynamic coefficients against time in a cycle were obtained and the experiment results were analyzed.

Polyimide nanofibers were obtained by electrospinning a solution of poly(amic acid)(PAA), a precursor of polyimide(PI) prepared in the laboratory, in dimethylacetamide(DMAc) at 14kV, followed by thermal imidization. Mechanical property of the resulting nanofiber non-woven membranes was investigated by tensile tests. Chemical structure and surface morphology of the non-woven mats were characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) as well as atomic force microscope (AFM) respectively.