Dielectric properties of marsh vegetation

The present work is devoted to the measurement of the dielectric properties of mosses and lichens in the frequency range from 500 MHz to 18 GHz. Subjects of this research were three species of march vegetation – moss (Dicranum polysetum Michx), groundcedar (Diphasiastrum complanatum (L.) Holub) and lichen (Cladonia stellaris). Samples of vegetation were collected in Tomsk region, Western Siberia, Russia. Complex dielectric permittivity was measured in coaxial section by Agilent Technologies vector network analyzer E8363B. Green samples was measured for some moisture contents from 100% to 3–5 % during a natural drying. The measurements were performed at room temperature, which remained within 21 ÷ 23 ° C. The frequency dependence of the dielectric constant for the three species of marsh vegetation differ markedly. Different parts of the complex permittivity dependency on moisture were fitted by line for all frequency points. Two break point were observed corresponding to the transition of water in the vegetation in various phase states. The complex permittivity spectra of water in the vegetation allow determining the most likely corresponding dielectric model of water in the vegetation by the method of hypothesis testing. It is the Debye’s model. Parameters of Debye’s model were obtained by numerical methods for all of three states of water. This enables to calculate the dielectric constant of water at any frequency range from 500 MHz to 18 GHz and to find the parameters of the dielectric model of the vegetation

Computer simulation of processes of radiation-thermal heating

In this work we present results of computer simulation of radiation-thermal heating of magnetic materials to change their structure. The energy source is a pulsed electron accelerator. The simulation results are presented in the form of the temperature distribution in the irradiated material, depending on the pulse duration, pulse repetition rate and the parameters of the material

Features of the permeability spectra of CoZnW hexaferrites in the spin-reorientation phase transition region

Abstract—The hexaferrites of the Co2-xZnxW system have a number of outstanding properties among other hexaferrites. This makes them promising both for obtaining new physical data and for practical use. In this paper, we analyze the concentration and temperature dependences of the resonance frequencies of natural ferromagnetic resonance and the damping constant in the equation of motion of the magnetization vector of these materials in the vicinity of spin-reorientation phase transitions. It is shown that these hexaferrites can find practical application in the entire microwave frequency range

Effect of magnetic field treatment on the electromagnetic properties of polymer composite based on barium hexaferrite at microwave frequencies

Polymer composite materials are used in widely different areas of science and industry. It is possible to change electromagnetic properties of composite materials by external treatments. The present work focuses on the change of electromagnetic characteristics of barium polymer composite, which is exposed to the external magnetic field with different strength. Composite materials, containing 65 wt. % concentrations of barium hexaferrite (Z-type) powder with a linear size of less than 80 µm as fillers and epoxy resin as matrix were prepared. Reflection coefficients were measured by coaxial method at frequency range of 0.01 – 18 GHz. It was revealed that reflection coefficients of barium hexaferrite and epoxy resin composite are very sensitive to the values of external magnetic field. There is nonlinear dependence of the reflection coefficients on the values of external magnetic field. The optimum value of the strength of the external magnetic field was shown to be equal 4 mT. The Cramers-Kronig relations were used to recover the real parts of the permeability and correct the imaginary parts of the permeability

Analysis and reoperation of the magnetic permeability spectra of textured composite based on Z-type hexaferrite by using Cramers-Kronig relations

The frequency dependences of the magnetic permeability of textured composite based on Ba3Co2,4Fe23,2O41 ferrite are given. The magnetic permeability spectra were obtained by coaxial method in the frequency range 0.01–18 GHz. The expert judgement on the spectra was made by using Cramers – Kronig relations. It was shown, that the Cramers – Kronig relations can be used to correct magnetic permeability measurements by reciprocal recalculation of the frequency dependences of the real and imaginary parts

Characterization of porous glass-ceramic material as absorber of electromagnetic radiation

Investigations of a foam glass-ceramic material synthesized from raw siliceous earth material by the two-stage method at temperatures below 950°C have demonstrated the improvement of its physic mechanical properties in comparison with foam glass synthesized from glass cullet. This material actively interacts with microwaves and can be used for the development of protective screens reducing the adverse effect of microwaves on biological objects, anechoic chambers, and rooms with low level of electromagnetic background noise. Spectra of the transmission and absorption coefficients and of the complex dielectric permittivity for frequencies in the range 26-260 GHz are presented. The observed effects demonstrate the existence of regions with partial and total reflection arising on the glass-pore boundary and of the microwave interaction with ultradisperse carbon particles that remain after foaming with incomplete frothier transition from the soot to the gas phase

Electrophysical characteristics of water of the rivers of Siberia and Altai

The results of measurements of the complex permittivity at the range of 100 MHz - 40 GHz and the conductivity of the water out of the reservoirs of Tomsk and Kemerovo regions and the Altai Territory are presented in the article. The method of the open-end-coaxial was applied. The conductivity was measured with LCR-meter at a frequency of 100 kHz. All the measurements were performed at temperatures of 10°C and 23°C. The samples are varied significantly in the values of conductivity, which is related to the geographical sampling place. Differences in permittivity values are greater at the low temperature and low frequencies and at the same time they are also significant at the high temperature and at high frequencies. The results of this study in order to improve the reliability of the analysis of the pollution degree and water salt content of natural water reservoirs should be taken into account the measurement made at wide frequency range. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Interaction of microwave radiation with composites containing nanosized hexaferrite, multiferroics, carbon nanostructures and silicon binder

A new composite consisting of nanosized powders of hexaferrites BaFe12O19 (ВаМ), multiferroics Co1.6Zn1.4W+CaTiO3 (30%), carbon nanostructures (powder mixture of carbon nanotubes, fullerenes, squamous structures and amorphous carbon) and silicone binder absorbs microwaves. Varying the concentration of each component in the composite materials changes the characteristics of a coating from reflective to absorbing electromagnetic radiation. Adding a layer with multiferroics to a composite material significantly improves the coatings as protective layer fro

The foam-glass material for a radio frequency echoless chambers

The conducted experiment of foam glass modification by carbon nanotubes shows increased radio absorbing properties in comparison with a foam glass without additives. Addition of carbon nanodimensional tubes in number of 1,5 wt.% increases a tangent of dielectric losses angle by 2,5 times. The coefficient of electromagnetic radiation absorption in the range of frequencies of 120 - 260 GHz increases for a foam glass with carbon nanotubes (1,5 wt. %) twice in comparison with a foam glass without additives. The foam glass modified by carbon nanotubes is recommended as the effective radio absorbing material for the device of anechoic cameras. This material is fire safety, nonflammable, environmentally friendly, rather light-weight

Quasi-optical 2D system for non-contact non-destructive testing of defects in natural and artificial crystals

The results of development the automated system of two-dimensional diagnostics of defects of crystalline materials are presented. Used technology imaging. The structural scheme of the system is given, its main blocks are indicated, the approbation process is described, the software of the system is described