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In order to employ periodic corrugated microstrip lines for reducing or suppressing electromagnetic interference in high‐speed or high‐frequency circuits, a precise method is necessary to calculate and measure the characteristic impedance of periodic microstrip lines. The equation for characteristic impedance (depending on frequency) of lossless periodic microstrip lines was obtained based on the transfer matrix method. A time domain pulse was used to measure the instantaneous impedance of conventional microstrip lines, and when the instantaneous impedance does not change with distance, it can be identified as the characteristic impedance of microstrip lines. However, when the time‐domain pulses are employed to measure the instantaneous impedance of periodic microstrip lines, rapid oscillations occur with distance. Therefore, a standard for spacing between adjacent grooves in the microstrip line can be suggested by analysing the interaction between the time‐domain pulses and the microstrip line grooves. Once such a standard is satisfied, many grooves etched along the microstrip line would no longer be distinguished by the time‐domain pulses. Such a principle and method can be used to determine the instantaneous impedance for the microstrip lines that have periodic grooves. On the other hand, when several periodic structures with different lattice constants coexist on a microstrip line, they can also be distinguished via the instantaneous impedance. A time domain reflectometer was used for measuring the instantaneous impedance of periodic microstrip lines, and the measured results are in agreement with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effectiveness of one stage vacuum sealing drainage (VSD) combined with bi-pedicle sliding flap transplantation in repairing open tibiofibular fracture and soft tissue defects of the lower leg., Methods: Twenty-five patients with open tibiofibular fracture and soft tissue defects of the lower leg were treated by VSD combined with bi-pedicle sliding flap transplantation between January 2012 and July 2014. There were 18 males and 7 females, aged 12-65 years (mean, 35.2 years). The injury causes included traffic accident injury (20 cases), falling injury from height (3 cases), and heavy pound injury (2 cases). The left side was involved in 14 cases, the right side in 8 cases, and both sides in 3 cases. According to Gustilo classification, injury was rated as type II (6 lower extremities), type III a (19 lower extremities), and type III b (3 lower extremities). The anterior tibial defect area after debridement ranged from 6 cmx3 cm to 12 cmx5 cm. The course of injury and admission was 1-18 hours (mean, 4.5 hours). An anterior tibial bi-pedicle sliding flap of 24 cmx6 cm to 48 cmx8 cm was designed to cover the wound and tibia fracture was fixed with minimally invasive internal fixation. After suturing the anterior tibial wound without tension, the flap was transferred forward. The exposed fibula was fixed with reconstruction plate. The remained wound was covered by VSD. Continuously antibiotic saline irrigation was applied postoperatively. After 15 days, the VSD dressing was removed and free skin graft was used to cover the remained wound., Results: After the VSD dressing was removed, the wounds and tension-reduced wound of 18 lower extremities completely healed. Unhealing wounds were covered by skin graft in 9 lower extremities. Infection occurred in 1 lower extremity and was cured after treated with antibiotics. All the wounds healed and flaps survived. The patients were followed up 6-24 months (mean, 18 months). The fractures union was confirmed by X-ray and the average union time was 3.2 months (range, 2.5-5 months)., Conclusion: The application of one stage VSD combined with bi-pedicle sliding flap transposition is a simple and safe treatment regimen for Gustilo type II-IIIa open tibiofibular fracture and soft tissue defects of the lower leg. It has the advantages of few complications and low costs, short hospitalization, and good effectiveness.