RESUMO
The tiny magnetic steel pair (TMSP), composed by two tiny magnetic steel blocks (TMSBs), is critical for some precision instruments. Incorrect matching of TMSP may result in insufficient instrument performance. Herein, the matching method of TMSP based on the Kuhn-Munkres algorithm is proposed. Further, an automatic TMSP matching device is developed. Especially, an ingenious clamp for multiple constraints of TMSB is presented and a visual/magnetism/force hybrid control strategy is realized for the safe and efficient manipulation of TMSBs in a magnetic environment. Moreover, with the TMSBs of a pendulum accelerometer, the matching experiments are conducted to validate the comprehensive performance. The result of the numerical experiment shows that the Kuhn-Munkres algorithm-based method is stable and efficient. The results of measurement and TMSP matching experiments show that the device has good repeatability (<1 mT) and practicability. The proposed matching method has great application prospect in various matching and microassembly of TMSPs.
RESUMO
Three maize male sterile mutants were obtained from the offsprings of two maize inbred lines 18-599 and 08-641, which were carried into space by the Shijian 8 Satellite. The stability of male sterile expression was observed in different locations, years, and seasons. In order to analyze the genetic characteristic of male sterility, testcross, backcross and reciprocal cross were made with these male sterile plants. The results showed that the male sterility character was stable in different locations, years, and seasons, and the sterility was inheritable. Because the maintainer lines and restorer lines for these sterile materials were found, and there was no male sterile plant separated among the reciprocal cross F2. Thus, we concluded that these mutants could be cytoplasmic male sterile. Combining the results of male fertility restoration test and PCR analysis, we could conclude that the three male sterile mutants were classified into the CMS-C type in maize. Owing to their difference in fertility restoration, these mutants may belong to different subgroups of CMS-C type. The discovery of the three male sterile mutants increased the genetic diversity of CMS-C type, improved the tolerance to Bipolaris maydis, and laid a foundation for extensive application of CMS-C in seeds production.
