电路板中电子元器件的手工焊接方法分析

本文首先介绍了手工焊接技术的基本原理——锡焊机理,列举了焊接前应做好的准备工作;其次重点讲解了手工焊接的五步操作法,并针对印制电路板的组成特点,讲述了电子元器件的成型、安装顺序及焊接注意事项,而后详细阐述了焊点质量检测的方法并分析常见十种有缺陷焊点的形成原因;最后,归纳总结手工焊接应掌握的技巧。     

The quantification of joint laxity in dancers and gymnasts

The aim of this study was to determine the range of movement in gymnastic and dance populations. Sixty-five participants (41 females, 24 males; mean age 21.4 years) were assessed. The sample included dancers and gymnasts ranging from novice and club standard to international and professional status. Non-specialized physical education students acted as controls. Range of movement was measured at the shoulders, hips, lumbar spine and ankles using a Loebl hydrogoniometer, and inherent joint laxity was assessed using Beighton and coworkers' adaptation of the Carter and Wilkinson 9-point scale. The right and left sides of the body were assessed and measures of active and passive motion were recorded. A graded increase in laxity was observed from controls, through novice gymnasts, to dancers and finally international gymnasts. The greater laxity of females than males was also confirmed. Dancers and gymnasts had a greater passive range of movement in all joints, which was partly inherited and partly acquired. There was a large difference between their active and passive ranges, which appeared to render the joints unstable.