Radiophysical Characteristics Research Articles

ANALYSIS OF THE TECHNOLOGY OF GENERATING MICROWAVE RADIATION WITH THE DEFINITION OF AN ADAPTIVE TYPE OF DIODES FOR THE FURTHER DESIGN OF DEVICES FOR DISINFECTION

The need to find an actual method of decontamination of grain products is more relevant than ever in our time. The needs of agro-producers should be embodied in multifunctional devices that give the opportunity to influence not only the aspect of disinfection, but also would allow to stimulate biological processes. This technique includes the use of ultrahigh-frequency (UHF) radiation. Installations used to solve decontamination issues have one main similar feature, namely the use of diodes in the generation system. Considering the main typical design of the microwave generator, it is possible to observe the main problem of the losses of the useful effect of the generation system - these are the losses in the diodes. For high-quality use and implementation, it is necessary to take into account the quality of processing of grain products, high indicators can be achieved due to the use of radio equipment. Modernization generally occurs by replacing the outdated generating part of the installation with a new one with better technical performance and greater variability of frequency and power ranges. First of all, what this tells us is that each crop has its own radio-physical characteristics, this factor is important for increasing processing efficiency. Studies show that the flexibility and controllability of the plant for agricultural processing is ensured by the use of modernized diodes. The paper examines the main types of diodes used in generating units, describes the main three loss zones, in general and directly in the avalanche diode (Reed diode). During the study of losses, the materials used in semiconductor technology were superficially considered in order to improve the conductivity of the diode. On the basis of the conducted research, reasonable conclusions were made in accordance with the topic of the research. The basic element of the installation is the use of pulse generators, but the use of outdated generators is irrational and pointless. It is clear that the success of this processing method depends on the development of radio technology. Continued efforts in this direction will help preserve and improve the effectiveness of this technology.

THE METHOD OF ADJUSTING THE MULTI-FREQUENCY PROBING RADAR SIGNAL PARAMETERS AND THE TROPOSPHERIC RADIO WAVEGUIDE CHARACTERISTICS

Peculiarities of air circulation in the coastal zone of large reservoirs (large lakes or inland seas such as the Black and Azov Seas) can lead to a significant departure from the standard spatial distribution of meteorological and, accordingly, radiophysical characteristics of air.
 As a result, it is possible for regions of space with an abnormally low attenuation level of radio waves of certain frequency ranges to appear – tropospheric radio waveguides (TWG). The appearance of TWG leads to multi-beam propagation of radio waves and fluctuations of radar signals. Fluctuations of the radar signal lead to a decrease in the range of detection of aerial objects by radars. For single-frequency radar signals, it is only possible to estimate the degree of distortion and the amount of radar detection range loss. A paradoxical situation arises when, due to TWG, it is possible to increase the range of detection of aerial objects, but due to the distortion of the radar signal in TWG, the detection performance decreases. For multi-frequency signals, it is potentially possible to adjust the parameters of the radar signal with the parameters of the radar channel (in this case, the tropospheric radio waveguide).
 The adjustable parameters of a multifrequency signal include: the number of frequency components; bandwidth of the frequency component; average frequency of the frequency component; signal duration; period.
 The characteristics of TWG, on which the parameters of the multifrequency signal depend, include: the lower transmission frequency of TWG; the upper transmission frequency of TWG; the delay time of the rays in the TWG.
 The bandwidth and beam delay values can be obtained directly by emitting and receiving a test multi- frequency pilot signal, but this method requires the presence of a reference reflector in space, which is difficult to implement in practice.
 The electrophysical characteristics of the tropospheric waveguide can be determined from the data of meteorological observations. The method developed in the article allows, based on the known characteristics of the tropospheric waveguide, to determine and adjust the parameters of a multi-frequency signal, which reduces the fluctuations of the sounding signal and increases the aerial objects detection rang.

Влияние гранулометрического состава и солёности на вид диэлектрических спектров грунтов

The permittivity data of several soil's types differing in particle size distribution and salt content are presented. The effect of humidity, granulometric composition, and salt content on the form of the spectrum of the complex dielectric permittivity are described. The general description of the mechanisms that influence on the dielectric characteristics of the samples under study is given. These dependences can be used in assessing the radiophysical characteristics of the underlying surface in the study of radiophysics and radiowaves propagation o problems.

Measuring the reflection of electromagnetic waves from foam structures of varied foaming ratio

A specific multi-frequency technique for measuring the reflectivity of constantly collapsing foam structures of varied initial foam ratio is developed. A measuring and computing complex implemented the technique is used. It operates in the microwave range from 38 to 52 GHz. Dynamic foam structures with an initial foaming ratio of 55, 108, and 156 units in the form of flat-layered foam samples with a fixed thickness are under measurement. It is shown that the use of foam structure covering allows to reduce the reflection of electromagnetic waves from metal surfaces significantly. The obtained measurement results confirm the possibility of measuring dynamic foam structures, and this technique makes it possible to separate reflections from the front and back faces of the samples, which is very important for the study of the syneresis processes of the foaming liquid and the destruction of foam structures. The results are useful for studying the radiophysical characteristics of foams and for developers of new foaming agents for various applications where electromagnetic waves are used.

Working out the Method of Obtaining Radio-Absorbing Composite Material Based on Magnetite Nanoparticles and Polydimethylsiloxanes

The work presents the investigations of working out the method of obtaining radio-absorbing composite material based on magnetite nanoparticles and polydimethylsiloxanes. The electron microphotographs of nanoparticles were obtained and the radio-physical characteristics of material in the frequency band of 0.1-8 GHz were measured.

Principles of regular-shaped radome antennas study with a spherical scanner

The paper considers the characteristics determination method basing on amplifasometric measurements of near field of the «antenna-radio-transparent radome» system with use of a spherical scanner. The method is based on determination of components of the amplitude spectra of homogeneous plane waves through the amplitudes of vector spherical waves of the tested antenna and the «antenna-radio-transparent radome» system. It is assumed that the radome has a regular surface shape and is a single-layer radome. The proposed method, in addition to determination of radiation characteristics, allows for the given antenna field polarization to determine the complex coefficient of passage thorough the radome as a function of spatial frequencies. It is also shown that it is possible to estimate the complex dielectric permittivity of a single-layer radome, both by calculating the components of uniform plane waves, and directly from the reduced field components on the outer surface of radome. Ways to study the radiophysical characteristics of theradom, are proposed.

The influence of a layered-inhomogeneous underlying surface on the antenna pattern

The results of works aimed at studying the influence of a flat-layered heterogeneous medium on the type of directional pattern of elementary wave emitter are presented. It was found that a change in the thickness of the frozen soil layer leads to a change in the directional characteristics of elementary emitter. The largest changes in the type of radiation pattern are observed when the thickness of the frozen / thawed layer is a quarter of the wavelength in this medium. It is shown that a change in the type of radiation pattern is also associated with the radiophysical characteristics of the underlying surface on which the antenna is located. The obtained results can be used in the process of optimizing the operation of antenna-feeder devices in conditions of changing the state of the underlying surface.

The influence of the underlying terrain on the directional characteristics of the HF-range antennas

The results of modeling the antennas directional characteristics in the HF range are presented. In the process of modeling, the radiophysical characteristics of the underlying surface measured under laboratory conditions were taken into account. The simulation results are compared with the results of field measurements of the antennas radiation patterns.

Composite Radio-Absorbing Coatings Based on Ferrimagnetic Fillers

Results from studying the crystalline anisotropy and magnetization saturation of hexagonal ferrites doped with a complex of diamagnetic ions are presented. The technological parameters of introducing different impurities that affect the radiophysical characteristics of hexaferrites are given. The main dependences of the synthesized material’s parameters on the means of ferromagnetic filler production are considered.

Water Vapor Radiometer: Measuring Instrument of Atmospheric Brightness Temperature

Results are presented for pilot studies of the error in measuring atmospheric brightness temperature at frequencies 20.7 and 31.4 GHz in the vicinity of water vapor emission lines. The accuracy of atmospheric brightness temperature measurements was evaluated using the water vapor radiometer at the Zelenchukskaya observatory. Measurements were made using the PNShI200 wide-aperture low-temperature noise generator, a working standard for the unit of equivalent noise temperature. The requirements for radiophysical characteristics and accuracy of reproduction of a unit of noise temperature were formulated for prospective reference wide-aperture low-temperature noise generators.

Radio-absorbent Material Based on Polyvinyl Chloride Filled with Disperse Carbon Fibre

The influence of the content of plasticiser and disperse carbon fibre on the radiophysical characteristics of filled film radio-absorbent materials is investigated.

Effect of Fibrous-Porous Composite Composition on its Radiophysical Characteristics

A multilayer fibrous-porous composite based on a non-woven fabric and a protective-decorative coating modified by carbon fibers was produced. The frequency dependence of the reflection coefficient for SHF electromagnetic radiation was studied as a function of the composition of the radio-absorbing material layers.

Study of the reflective characteristics of multilayered materials

The specific features of reducing the radar observability of aircraft by applying radar-absorbent materials are studied. A method for determining the reflective characteristics of different types of materials based on the Fresnel equations is considered. A good agreement between the radiophysical characteristics of multilayered materials calculated using this method and those obtained based on analytical solutions is demonstrated.

Influence of microstructure on properties of Ni–Zn ferrite radio-absorbing materials

In this work there have been carried out studies in the radiophysical characteristics of the samples of Ni–Zn ferrite radio-absorbing materials, obtained by the ceramic method under different technological conditions. There has been established the influence of microstructure on the electromagnetic losses of Ni–Zn ferrite radio-absorbing materials. The results indicate that the coarse-grained structure leads to an increase of radio-absorbing capacity at frequencies below 30MHz. It can be explained by the resonance of domain boundaries.

<sup>89</sup>Zr-PET Radiochemistry in the Development and Application of Therapeutic Monoclonal Antibodies and Other Biologicals

Positron emission tomography with (89)Zr can be used to follow the behaviour of therapeutic monoclonal antibodies (mAbs) and other biologicals in vivo. The favourable radiophysical characteristics of (89)Zr allow multiple days PET scanning after injection. For the coupling of (89)Zr to proteins six desferrioxamine (DFO)-based bifunctional chelators have been described, five of which forming stable complexes in vivo. Of the methods that give stable complexes three are based on random lysine modification of mAbs and two on site-specific engineering. Up to now only two methods, random lysine modification with N-suc-DFO or DFO-Bz-NCS, have been used in clinical studies. In this review firstly aspects of the physicochemical properties and production of (89)Zr are emphasized as well as important items that have to be taken into account for current good manufacturing practice (cGMP) compliant production of (89)Zr-labeled proteins. Next, the different DFO-based conjugation strategies will be discussed with respect to synthesis, and their (pre)clinical evaluation particularly in the field of oncology.

Nonlinear effects in corundum and ilmenite in high frequency electromagnetic fields

This paper details the results of a comparative study of two materials having the same structure, but drastically different radiophysical characteristics. Corundum ceramic samples were synthesized from pure substances by firing a charge in air at 1450°C for 1 h. The second material was prepared from natural ilmenite without heat treatment using an epoxy polymer binder. Measurements of the transmission and reflection factors within the frequency range of 8–26 GHz indicate that corundum ceramic samples scatter electromagnetic radiation (EMR) exhibiting a pronounced dispersion of the reflection and transmission factors. On the contrary, ilmenite samples absorb EMR showing no dispersion at all. The differences in the radiophysical characteristics are due to the presence of magnetic impurities in the crystal lattices of corundum and ilmenite and the specific features of the spin-phonon interaction in dielectric and ferrite materials.

A Pilot Study of Trans-Arterial Injection of166Holmium-Chitosan Complex for Treatment of Small Hepatocellular Carcinoma

Percutaneous approaches, such as percutaneous ethanol injection and radiofrequency ablation, have been most widely used for hepatocellular carcinoma patients who were not eligible for surgery. New technologies to improve the efficacy are currently needed. 166Holmium is a neutron activated radionuclide, and has several beneficial radiophysical characteristics for internal radiation therapy. 166Holmium-Chitosan complex, in which chitosan is chelated with 166Holmium, was developed as a radiopharmaceutical for cancer therapy. We have conducted a pilot study to evaluate the clinical efficacy of transarterial administration of 166Holmium-Chitosan complex in patients with a single and small (< 3 cm) hepatocellular carcinoma. 166Holmium-Chitosan complex, at a dose of 20 mCi per cm of tumor mass-diameter, was administered through the artery that directly fed the tumor. Twelve patients were treated with a median follow-up duration of 26 (range: 12-61) months. The tumor diameter ranged between 1.5 and 2.5 cm. Ten patients (83%) had complete response and two (17%) had partial response. The median complete response duration was not reached. The median AFP level declined from 83.8 to 8.3 ng/mL within 2 months after treatment. No grade III/IV toxicity was observed. Grade I and II toxicities were observed in four patients (2 abdominal pain, 1 fever, and 1 AST/ALT elevation). No toxic death occurred. This preliminary study shows a promising and durable complete response rate with an acceptable safety profile. Further studies with greater accrual of patients are warranted.

Inverse problems of the nonlinear electrodynamics of high-T c superconductors

A method is developed for reconstructing the dependence of the surface impedance of Zs(H) of high-Tc superconductors (HTSCs) on the amplitude of an ac magnetic field from measurements of the nonlinear radiophysical characteristics of microwave HTSC resonators. It is shown that the nonuniformity of the structure of the electromagnetic field in a resonator lead to integral equations for Zs(H). The corresponding integral equations are obtained for certain types of resonators. The errors of the conventional methods employing algebraic relations for Zs(H) are analyzed. The Tikhonov regularization method, developed in the theory of ill-posed inverse problems, is used to reconstruct the functions Zs(H) from the integral equations. Numerical experiments on the reconstruction of Zs(H) were performed, and the requirements for the accuracies and other characteristics of the experimental data were determined from them.

Synthesis of new bifunctional chelating agents: (1R*,2R*,4S*)-4-isothiocyanatocyclohexane-1,2-diamine-N,N,N′,N′-tetrakismethanephosphonic acid (4-ICMP) and (1R*,2R*,4S*)-4-isothiocyanatocyclohexane-1,2-diamine-N,N,N′,N′-tetrakisethanephosphonic acid (4-ICEP)

Immunotherapy with radiolabelled antibodies should allow fairly specific targeting of certain cancers. Although 153Sm possesses favourable radiophysical characteristics for such therapy, a lack of radiolabelling stability in vivo limits its application. Yet the use of phosphonic semi-rigid bifunctional chelating agents (BCA) can improve its stability. Syntheses of (1R*,2R*,4S*)-4-isothiocyanatocyclohexane-1,2-diamine-N,N,N′,N′-tetrakismethanephosphonic acid (4-ICMP) and (1R*,2R*,4S*)-4-isothiocyanatocyclohexane-1,2-diamine-N,N,N′,N′-tetrakisethanephosphonic acid (4-ICEP) are described in this paper. The complexing properties of these two compounds has been confirmed by labelling with 153Sm. A novel synthetic approach involving the introduction of methanephosphonic functions has also been developed.