Active control of terahertz waves based on hybrid VO periodic corrugated waveguides.

We describe a method for the active control of terahertz (THz) waves using hybrid vanadium dioxide (VO) periodic corrugated waveguide. Unlike liquid crystals, graphene and semiconductors and other active materials, VO exhibits a unique insulator-metal transition characteristic by the electric fields, optical, and thermal pumps, resulting in five orders of magnitude changes in its conductivity. Our waveguide consists of two gold coated plates with the VO-embedded periodic grooves, which are placed in parallel with the grooves face to face.

[Quality comparison between two cultivated Chinese yam-Kunming yam and Tiegun yam].

Objective: To compare the quality of cultivated Chinese yam (Dioscorea polystachya Turcz.) from Yunnan (Kunming yam) and Henan (Tiegum yam) by determining the content of dry substance in fresh sample and the contents of water extracts, ethanol extracts, starch, protein, crude-fat and polysaccharide in dry sample.

Method: The above-mentioned indexes were determined by methods of air desiccation, cold-immersing, hot-immersing, iodine-blue coloration, half Micro-Kjeldahl, Soxhlet extraction and spectrophotometric method respectively.