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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]

A prototype for a low temperature solar-driven biogas steam reforming process was designed by coupling a hydrogen selective membrane reactor and linear Fresnel collector technology. To verify the prototype, the membrane reactor model was established by using ASPEN Plus and was studied using a modelled biogas in the temperature range 450 to 500oC. The methane conversion was significantly enhanced by applying the H2 selective membrane. Based on the actual Direct Normal Irradiation in South Africa, the capability of linear Fresnel collector was verified for the required heat duty in this study, which varying from 90.1 to 366.4 kW/m2. This novel work constitutes a reference study for new developments with reactor designs and solar energy application in biogas steam reforming processes.