Abstract-The PMCT probe, saying, one kind of open-ended coaxial probe adopted widely in microwave coagulation therapy of cancer, has been used to measure the complex permittivity of freshly excised specimens of normal animal tissues. The RFM model for PMCT probe is developed to extract the anticipant permittivity of specimens under test.In addition, the effects of several factors on the measurement results have been considered and discussed, including different temperature and reference materials, as well as the sampling frequency range and intervals of the rational function model. All the experiments have been conducted at the microwave frequency range from 450 MHz to 14.5 GHz.
Global warming has been reported to cause reductions in crop yields. However, it was suggested that warming temperature might benefit crop productivity in some cool areas at high latitude. In this study, we conducted a 17‐year field experiment (2002–2018) on spring wheat in Inner Mongolia. Temperature changes during each growth stage of spring wheat were investigated. Responses of spring wheat yield to temperature changes during the specific growing stages were evaluated. Average annual maximum temperature (Tmax) and minimum temperature (Tmin) significantly increased over the past 17 years. However, Tmax did not show obvious increase trend during spring wheat growing seasons (p = 0.0672). Furthermore, Tmax also had no distinct change before or after anthesis. Tmin significantly increased during the whole growing season, as well as in pre‐ and post‐anthesis stages. Correlation analysis indicated that Tmax in the entire growing season and post‐anthesis did not affect spring wheat yield, but high Tmax during pre‐anthesis can improve grain yield. The Tmin during the life cycle and pre‐anthesis both had positive relationship with grain yield. Moreover, elevated temperature from seedling to stem elongation can benefit tiller formation and thus increasing spike number, which contributed to the significant yield increase (p = 0.0093). Overall, climate warming affect spring wheat yield in cool area, and increasing temperature that was below the optimum temperature can benefit wheat productivity.
The resonant cavity perturbation technique is usually used to measure the complex permittivity of various dielectric materials at microwave frequency. The values of real and imaginary part of the complex permittivity of the material under test can be deduced from the measured shift of resonant frequency and the change of quality factor (Q factor) of the resonance cavity with inserted samples. In this article, an improved resonance cavity perturbation technique is employed to measure the complex permittivity of biological materials, including porcine fat, marrow, and liver, etc. The measured results agree well with the known data, demonstrating the potential validity of our method. This method can be expected to extend to permittivity measurement of other biological material even the tissues from human body.
ABSTRACT:We review three commonly used conditions that characterize negative refraction in isotropic dielectric-magnetic materials. We show that while all the different conditions are equivalent for passive media, they are distinct for different types of active media.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.