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A hydroponic experiment was performed to investigate the mechanisms of Se mitigation of Cd toxicity in oilseed rapes. The effects of 0.3 mg·L-1 Se on Cd accumulation, photosynthetic characteristics and activities of antioxidant enzymes in two genotypes of rape (WH-19 and WH-95) under 0.5 mg·L-1 Cd stress were studied. The results showed that: Se application significantly decreased Cd contents in roots, stems and leaves in WH-95 with the decrease rates of 8.51%, 34.61% and 46.14% respectively compared with only Cd treatment, while no significant differences were observed in WH-19. Se greatly increased the net photosynthetic rate and the transpiration rate by 18.96% and 22.77% respectively, and significantly decreased the intercellular CO2 concentrations to 72.61% in WH-19 compared with only Cd treatment. As for WH-95, only the intercellular CO2 concentrations were significantly decreased to 85.96% under Se application, while other three photosynthetic characteristics showed no greatly changed; Se significantly decreased SOD activity in WH-19 by 29.03%, while no significant differences were observed in the activities of CAT and POD; For WH-95, 9% increase was found in CAT activity, while no marked differences were found in the activities of SOD and POD compared with only Cd treatment. Overall, Se alleviated Cd toxicities in the two oilseed rapes by enhancement of the photosynthetic system. However, the Cd accumulation and the antioxidative system showed differenct responses to Cd stress.

On the basis of biological visual systems and object recognition technologies,several key technologies of artificial compound eyes,including its structure,splicing,fiber coupling and optical signal receiving technique were studied and a bionic compound eye receiving system was designed for staring laser radars.By imitating the structures and shapes of compound eyes of insects,the system consists of 16 lens arrays,and its whole field angle is 2 °.The optical system was designed by the Zemax software and optical signals were received by fiber coupling technology.The detection results were studied experimentally,and it shows that this receiving system can well reflect the contour of a detecting target,and the detection range is more than 200 m.On the experimental setup,a range image with 20 frames is obtained,and the pixel space is 1.72 m×1.72 m.Obtained results verify the feasibility of proposed system and indicate that the system can be used in the missile end-guiding and the topographic matching of aerocrafts in low altitudes.

A new method of optical control is put forward based on conical effect in biaxial crystal.When the incident light spread along optical axis direction,the propagation direction will change with the polarization direction.By controlling the magnetic field on the magneto-optic modulator,the polarization direction can be changed,thus the laser beam direction control is realized.The fundamental of disk tracking is analyzed and overall plan is also designed,the relationship between polarizing angle and tracking displacement is obtained by numerical simulations,so this plan is reasonable.Compared with traditional tracking means of machine-electricity,this kind of plan has the following advantages:light weight,small volume and fast transient response.A new method for optical switch and scanning is provided meanwhile.

Based on the principle of hollow ring achieved by conical refraction effect in biaxial crystal,the formula of phase difference distribution between every point and the minimal point in the hollow ring are deduced,and the regularity of phase difference distribution is obtained by means of simulations.The continuity in the circumference of polarization direction variation of each point in the hollow ring is proved.In the experiment,un-polarized He-Ne laser is adopted to perpendicular radiate KNbO3 crystal,then polarization characteristic of hollow beams achieved by conical refraction effect in biaxial crystal is tested.The result of theoretical analysis agrees well with experiment.

The high repetition electro-optical Q-switched red laser is studied based on the polarized characteristic of Nd:YAP crystal.The parameters of the three-mirror folded are optimized by the thermal focus length of Nd:YAP crystal.The electro-optical Q-switched of LN crystal and typeⅡnoncritical phase-matching intracavity frequency-doubling of KTP crystal are adapted.Then the output peak power with 28.3 kW,about 76 ns of pulse duration at 670 nm and the frequency doubling efficiency of 37.1% are obtained in the condition of 75 A pump current and the electro-optical Q-switched repetition rate of 1 kHz.

A novel hybrid cascade asymmetric inverter is developed in this paper. The novel inverter is based on connection of multiple single-phase asymmetric 5-level inverter modules. With the dc bus voltage ratio V1:V2=1:2, the phase voltage of the novel inverter with two modules per phase will output 13 voltage levels. A new hybrid asymmetric control technique for the inverter is proposed. Spectral analysis of the phase output voltage is carried out. According to the spectral analysis, there is no real power exchange between modules in a phase leg. A two-module three-phase inverter was constructed in the laboratory, experimental results are presented as well as comparison with hybrid diode-clamp cascade inverter is given

This paper proposed a novel hybrid asymmetric 9-level inverter in which an asymmetric 5-level inverter and an H-bridge inverter with equal DC bus voltage are series connected to form an inverter phase leg. A new hybrid asymmetric control technique for the novel inverter is proposed. Analysis of output spectral and DC bus voltage unbalancing problem is carried out digital controller design is presented. Simulation and experiment results are provided.