The ion transit effects on the sheath dynamics inthe intermediate radiofrequency regime: excitationsof ion-acoustic waves and solitons

The capacitively coupled plasma is investigated kinetically utilizing the particle- in-cell technique. The Argon (Ar) plasma is generated via two radio-frequencies. The plasma bulk density increases by increasing the voltage amplitude of the high frequency (≥ 13.56 MHz) which is much greater than the ion plasma frequency. The intermediate radio-frequencies ( ≈ 1 MHz) which are comparable to the ion plasma frequency causes a broadening of the ion energy distribution considerably, i.e., ions gain energies above and lower than the time-averaged energy. The good agreement between published experimental results and our theoretical calculations via the Ensemble- in-Spacetime model confirms the modulation of ions around time-averaged values. Intermediate frequencies allow ions to respond partially to the instantaneous electric field. The response of ions to the instantaneous electric field is investigated semi- analytically. The dispersion relation of the plasma sheath and bulk are derived. Stable ion acoustic modes are found. The ion-acoustic modes have two different velocities and carry energy from the sheath edge to the electrode. Also, intermediate frequencies excite solitons in the plasma sheath; the results may help to explain the ion density, flux, and energy modulation, and, consequently, the broadening of the ion energy distribution.

Magnetogenesis and the Cosmic Web: A Joint Challenge for Radio Observations and Numerical Simulations

The detection of the radio signal from filaments in the cosmic web is crucial to distinguish possible magnetogenesis scenarios. We review the status of the different attempts to detect the cosmic web at radio wavelengths. This is put into the context of the advanced simulations of cosmic magnetism carried out in the last few years by our MAGCOW project. While first attempts of imaging the cosmic web with the MWA and LOFAR have been encouraging and could discard some magnetogenesis models, the complexity behind such observations makes a definitive answer still uncertain. A combination of total intensity and polarimetric data at low radio frequencies that the SKA and LOFAR2.0 will achieve is key to removing the existing uncertainties related to the contribution of many possible sources of signal along deep lines of sight. This will make it possible to isolate the contribution from filaments, and expose its deep physical connection with the origin of extragalactic magnetism.

Designing a Spectrum Allocation Chart for Nigeria

The regulation of the radio spectrum today by government agencies addresses the issue of interference between radio stations by allocating, allotting and registering bands of radio-frequencies. The framework of management is done at the international, regional and national level. With this paper, we present a study of the radio spectrum allocation policies in some leading countries and Nigeria. However, narrowing the study down to the detailed design of spectrum allocation charts. The study used the information in the national table of frequency allocation (NTFA) to design the spectrum allocation chart of Nigeria with Photoshop application. The spectrum allocation chart was designed with high resolution for high zoom capabilities so that researchers can gain a quick overview of the radio services allocated in the radio spectrum in Nigeria.

THE PROBLEM OF REDISTRIBUTION OF RADIO FREQUENCY USED IN THE ORGANIZATION DIVISIONS

The problem of radio frequency distribution is considered in the article, taking into account the regulations and geographical location of the operating units. The problem of assigning radio frequencies from among those assigned for corporate use is studied. Using conformal mapping, it was substantiated that any territory can be divided into zones, each of which will have a border with only three other zones. In this case, in each zone, you can assign frequencies in the amount of one quarter of the total number of available frequencies that do not overlap with frequencies assigned to adjacent zones. A mathematical model of the problem of radio frequency redistribution has been built, taking into account the regulations and the geographical location of the units. The implementation of algorithm allows taking into account the history of frequency distribution by zones, which allows you to completely update the used radio frequencies for a new period of operation. A software module has been compiled that generates frequencies at random from those available for assigning corporate use for each zone. The software module allows fast and frequent reallocation of frequencies by zones, thereby ensuring the safety, reliability and stability of communication between organizational units.

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Edible fungi are rich in nutrition, but they are susceptible to spoilage, and often prolonged by drying. RF and microwave energy drying have the advantages of short drying time, high energy efficiency and good process control. However, to develop an effective dielectric drying method, it is important to understand dielectric properties, the major factor characterizing the interaction between the electromagnetic energy and the food. At present, there is a lack of research on dielectric properties of edible fungi. In this study, a vector network analyzer and an open-ended coaxial-line probe were employed to measure the dielectric parameters. The dielectric parameters were observed at different temperatures (25–85 °C) for edible fungi powder with moisture content ranging from 5 to 30% wet basis over a frequency range of 1–3000 MHz. The relationship between the dielectric properties and frequency, temperature, and moisture content were obtained via regression analysis. Further, the dielectric penetration depth was calculated, and the effects of frequency, moisture content, and temperature on the penetration depth were also analyzed. The results showed that the dielectric properties of edible fungi powder increased with an increase in moisture content and temperature, while they decreased with increasing frequency. At high moisture content and temperature, the increase in dielectric properties was slightly larger than that at low moisture content and temperature. The dielectric properties changed more evidently at lower radio frequencies than at higher radio frequencies. The penetration depth decreased with an increase in temperature, moisture content, and frequency. It can be concluded that a large penetration depth at radio frequencies below 100 MHz could be used to dry edible fungi on a large scale, whereas microwave energy could be employed for drying edible fungi on a small scale.

About some features of constructing fifth generation networks for civil aviation.

The article is devoted to the construction of 5G communication networks for aviation during landing/take-off. We describe the problem of building this network based on existing standards and the radio frequencies used. The main decision is that the implementation of this task requires the construction of a heterogeneous network, including various types of access networks operating in different frequency ranges, as well as implementing different requirements for the coverage of the mobile network.

Linking the optically bright Gaia frame to the third International Celestial Reference Frame

<p>The new data release of the Gaia satellite operated by the European Space Agency recently published its 3rd data release (Early Data Release 3, EDR3). The dataset contains astrometric data of about 1.8 billion objects detected at optical frequencies and therefore it outperforms any catalog of astrometric information up to date. The reference frame defined by Gaia EDR3 is aligned to the International Celestial Reference System by referring to counterparts in its realization, the third International Celestial Reference Frame (ICRF3), which is calculated from very long baseline interferometry (VLBI) observations of extragalactic objects at radio frequencies. <br>The Gaia dataset is known to be magnitude-dependent in terms of astrometric calibration. As the objects in ICRF3, although bright at radio frequencies, are mostly faint at optical frequencies, the optically bright Gaia frame has to be linked to ICRF3 by additional counterparts besides objects in ICRF3. The non-rotation of the optically bright Gaia frame is especially important as optically bright objects can, besides astrophysical studies, be used for navigation in space, where other geodetic systems like global navigation satellite systems are out of reach. Suitable additional counterparts are radio stars which are observed by VLBI relative to extragalactic objects in ICRF3. We discuss the orientation and spin differences between the optically bright Gaia EDR3 and VLBI data of radio stars and their impact on the Gaia data usage.</p>