Nowadays it is difficult to attract undergraduate students’ interesting to put sufficient time to learn major courses in China, which are too hard for them to quick grasp and fully understanding. Here we report a digital education reform for improving interactions between students and instructors, in which we transform the abstract, obscure and boring knowledge, such as physical, mathematical, electronic or optical concepts into direct and dynamic 3-D model and flash. Therefore, this method can convert theoretical concepts into easy understanding pictures. Our several years’ experience shows that this education mode can make students’ willing to think and practice, then it is helpful for attracting their learning interests. Most students benefit from this education mode which can greatly enhance their understanding abilities.
A practical plane-cone resonator for the high-power, transverse-flow CO2 laser has been designed. The output characteristics of the plane-cone resonator are researched experimentally and compared with a traditional plane-concave resonator. The output mode is an approximate TEM03 mode with a resonator length of 3 m and an equivalent aperture radius of 30 mm. The beam divergence angles of the plane-concave resonator and the plane-cone resonator are 2.6 and 2.1 mrad, respectively. In the experiments that studied the misalignment characteristics, the miss rates of the output beam are 16% and 8%, respectively, when the misaligned angles of the output mirrors are both 0.41 mrad. Also, the miss rates are 20% and 5%, respectively, when the misaligned angles of the reflectors are both 0.41 mrad. The results indicate that this plane-cone resonator has a better anti-misaligned stability than plane-concave resonators.
In this paper, a laser cutting technology for the oil pipes with the thickness of 10mm, the diameter of 142mm and the
material of N80 has been developed, in order to reduce the high hole-blast rate in processing. Experiments are taken on
the Rofin DC025 slab CO2 laser cutting system and a set of flexible fixtures. The reasons of forming blast-hole have
been analyzed, and the influences of technique parameters on blast-hole rate have been studied, such as laser power,
pulse frequency, laser delay, focus position and oxygen pressure. The results show that the blast-hole rate can be
controlled lower than 5% at the conditions of laser power 1500W, laser delay 5s, pulse frequency 180Hz, the oxygen
pressure 0.6 kg/cm2, focus length 190mm, nozzle diameter 1.5mm.