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Legged robots suffer from the impact due to the consistent collisions with the ground. At the moment of collision, the sudden impact force not only causes the legs to lose contact off the ground, but can also reduce controllability and durability. This phenomenon becomes worse for the robots in running. In order to mitigate such an impact effectively, this study focuses on the mechanical structure of the legs, unlike the previous studies, which focused on the component level. The mechanical structures include actuator configuration, segment ratio, total length, and flexion direction. Contact inertia (CI), closely related to the impact, is derived and utilized to analyze the mechanical structure in terms of impact mitigation. A series of impact experiments with a fabricated leg verify that the mechanical structure affects mitigating the impact.

The surgical closure of patent ductus arteriosus (PDA) is provided more frequently in extremely low birth weight babies who are usually deemed unsuitable for pharmacological closure. We have adopted subaxillary mini-thoracotomy in order to lessen surgical trauma in these babies; and its clinical results were analyzed. From April 2004 to August 2008, out of 50 babies at the neonatal intensive care unit who underwent the surgical closure of PDA, 22 premature babies weighing less than 1 kg at operation were included in the study. Eleven babies were males and mean gestational age was 27 weeks ranging from 23+3 to 30+2 weeks. Mean body weight at operation was 816 g ranging from 490 to 989 g and average age at operation was 17.9±11.9 days. Of them, 17 babies (72%) were ventilator dependent preoperatively, as compared with 13 out of 28 (46%) babies that weighed more than 1 kg (P<0.05). Four babies did not survive to discharge. Among 28 babies who were heavier than 1 kg, there were only one death. However, the mortality difference was not statistically significant (P=0.11). All mortalities were caused by inherent problems of prematurity and co-morbidities. Out of 17 babies who had been ventilator dependent preoperatively, 13 weaned off successfully at 17.0±23.9 days after the operation. The baby patients heavier than 1 kg weaned at 6.0±5.3 days (P=0.27). Surgical outcome of simple and less invasive subaxillary mini-thoracotomy was satisfactory; the surgery is highly recommended for ductal closure in extremely low weight premature babies.

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