Dynamic shearing high strain-rate experiments on three types of titanium alloy have been carried out by using a modified split Hopkinson bar. Microstructure and mechanism for grains refining in adiabatic shear band formed under the condition of high strain-rate were investigated by means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that the mechanisms for grains refining in adiabatic shear band of titanium alloy mostly consist of three sorts. They are the mechanism of breakdown of elongated grains which due to action of dislocations,and the mechanism of rupture of twins and the mechanism of dynamic recrystallization, respectively. The mechanism of dynamic recrystallization is the universal one for grains refining in adiabatic shear band of titanium alloy. The formation of refining grains is usually a result of combined action of several sorts of mechanisms.
Brush-cutter would always bring cutting shock in its cutting process, and its not easy to estimate the cutting resistance by usual cutting theory and methods. The present paper emulates real cutting process by using ANSYS/LS-DYNA, and orthogonal anisotropy model was used to symbolize the wood material. The result shows that the cutting tool with a 40 degrees rake is more competent than the ones with 30 degrees and 50 degrees. This result fits common cutting theories, thus the rationality of this research is proved, and a cutting resistance curve is obtained.
A novel water photovoltaic/thermal (PV/T) solar system was designed, which consisted of a flat plate solar thermal collector and a flat plate PV/T collector in parallel. The area of flat plate solar thermal collector and PV/T collectors were 2m2, respectively. The performance of PV/T solar system was tested under condition of flat plate PV/T collectors with glass cover. The test results show that the average output electricity power of PV/T solar system was 28.1W in sunny day at 8:27-17:00 (March 8,2013, at Chuxiong city), the water temperature in the water tank insulation with 200L was raised from 18°C to 60°C. The daily useful efficiency of the PV/T solar system reached 46%. The PV/T solar system could meet the basic need of ordinary families to lighting electricity and hot water. The PV/T solar system had high practicality and was suitable for ordinary rural families.
The safety of the six-state scheme in the practical communication systems was studied based on an effective eavesdropping method, which called path attacks adopted by eavesdroppers. In the practical systems, eavesdropper can select appropriate path to eavesdrop on legitimate users to obtain some information. This method will keep photon number distribution in the laser pulses, and the eavesdropper can be hidden by the losses of quantum channel without being detected. The results show that eavesdropper can get more information with the increase of transmission distance and the average number of photons.
In photoelectric micro-power supply integrated on chip, the conversion efficiency of solar cell was lower compared with canonical solar cell. In order to improve the conversion efficiency of the solar cell, three technologies (fabricating back surface field, fabricating surfaces texture and reflector) were adopted in integrated process of photoelectric micro-power supply on chip. The relevant theory of the three technologies was introduced. The optimum schedule of the photoelectric micro-power supply integrated on SOI wafer was proposed. The conversion efficiency of solar cells was analyzed by simulation tools (PC1D). The results prove the conversion efficiency of solar cells was improved from 9. 34% to 13.3%.
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