Radiation Frequency Research Articles

Phase shifter based on two-dimensional electron system on a dielectric substrate

We experimentally investigate phase shift gained by electromagnetic radiation transmitted through a two-dimensional electron system (2DES) on a dielectric substrate. We systematically examined the dependence of the phase shift on the radiation frequency and 2DES electron density for the GaAs semiconductor substrate. A theoretical approach was developed that found good agreement with experimental results. We demonstrate a practically achievable phase shift of 105°. Obtained findings pave the way for the design of terahertz devices that can manipulate the radiation phase in a controlled and precise manner.

Scientific equipment for the “Sun-Terahertz” space experiment: study of the temperature effect of the Golay cell

The future space experiment «Sun-Terahertz» is aimed at studying the Sun in the unexplored terahertz range, obtaining new data on the terahertz radiation of the Sun, solar active regions and solar flares. The scientific equipment being developed is a set of eight detectors sensitive to radiation of various frequencies in the range 0.4–12.0 THz. The Golay cell optoacoustic receiver was used as a sensitive element of the detectors. This paper examines the problem of changing the sensitivity of receivers of this type when their own temperature changes (temperature effect). Using a test bench based on a single-channel model of scientific equipment and a black body simulator, the linear section of the temperature dependence of the receiver was determined. A method for compensating the temperature effect of optoacoustic converters Golay cell has been developed and the results of its testing on a test bench are presented. This technique will be useful in the development of scientific equipment based on Golay cells, the operation of which is expected under conditions of temperature changes in the surrounding space.

Earthquakes Three-Stage Early Warning and Short-Term Prediction

Among the anomalous geophysical phenomena observed preceding earthquakes, specific attention has been given to VLF/LF, ULF (very low frequency/low frequency, ultra-low frequency) electromagnetic (EM) emissions, recorded before earthquakes, because of an interesting correlation between them and seismic activity. Numerous scientific papers have been published on this topic, providing convincing evidence of these processes observed using ground-based and satellite ground-based observations during the preparation for the earthquake. These phenomena are detectable both at laboratory and geological scales. The authors of this paper have used an avalanche-like unstable geological model of fault formation and a model of the generation of electromagnetic emissions detected before the earthquakes to prove the prediction capabilities of VLF/LF EM emissions. The first gives a clear imagination of earthquake preparation in all stages in the focal area from the beginning of the micro-cracks appearing to the final formation of fault. Another one, based on electrodynamics, explains the EM emissions origination process and offers a formula that analytically connects the observed frequency of EM radiation with the linear size of the emitted body (fault). It is worth emphasizing the synthesis and rather harmonious relation of the mentioned models. Based on the above models conducted studies clearly show that the description of a qualitative avalanche-unstable geological model of fault formation using VLF/LF EM radiation data made it possible to quantitatively characterize the full cycle of preparation and occurrence of earthquake process. Namely, in the case of VLF/LF emissions monitoring, the beginning of the “avalanche process” of ruptures is considered the first stage of early warning of an incoming earthquake. The so-called EM emissions “silence” period is assessed as the second stage of early warning. The third early warning or an alarm about an incoming earthquake may be announced immediately at the moment of the first anomaly appearance subsequently the “silence” period. This article offers the method of earthquake three-step early warning and short-term (hourly) prediction.

Very high frequency radiation emitted by negative narrow bipolar events occurred over malacca strait

In this paper, Very-High Frequency (VHF) radiation pulses associated with 11 negative Narrow Bipolar Events (NBEs) produced by a tropical storm over Malacca Strait are examined. The lightning data were recorded from a measurement station (ST) which consisted of a fast antenna (FA) and three VHF sensors (two 5 m perpendicular baselines interferometer). The average rise time (RT), average zero-crossing time (ZCT), average pulse duration (PD), and range of peak currents of the negative NBEs were 1.4 ± 0.4 μs, 2.7 ± 1.0 μs, 12.0 ± 6.9 μs, and −10 to −64 kA, respectively. The key finding is that all VHF radiation pulses have been found to precede the negative NBEs with an average lead time of 0.7 ± 0.3 μs. An interferometer map for one negative NBE (labelled as NBE10) detected at 35.7 km from ST has shown a characteristic of mixed propagation direction of fast streamers. The first VHF radiation source was detected at 12.4 ± 0.4 km above sea level. The total length and estimated velocity of the main propagation of the VHF radiation sources were 2.2 ± 0.7 km and between 1.4 × 108 and 2.8 × 108 ms−1, respectively. Moreover, based on the Himawari satellite image, the maximum extent of the cloud top height was estimated to be around 20.9 km over sea level (over Malacca Strait). All the VHF radiation sources associated with NBE10 were suggested to be detected above the main negative charge region (6 km altitude that corresponds to −10 °C). Thus, it could be suggested that NBE10 was initiated most likely in the environment of the ice crystals alone, based on the first altitude of the VHF radiation source and maximum extent of cloud top height.

Optical Shubnikov–de Haas oscillations in two-dimensional electron systems

We report on dynamic Shubnikov–de Haas (SdH) oscillations that are measured in the optical response, subterahertz transmittance of two-dimensional systems, and reveal two distinct types of oscillation nodes: “universal” nodes at integer ratios of radiation and cyclotron frequencies and “tunable” nodes at positions sensitive to all parameters of the structure. The nodes in both real and imaginary parts of the measured complex transmittance are analyzed using a dynamic version of the static Lifshitz-Kosevich formula. These results demonstrate that the node structure of the dynamic SdH oscillations provides an all-optical access to quantization- and interaction-induced renormalization effects, in addition to parameters one can obtain from the static SdH oscillations. Published by the American Physical Society 2024

Boosting radio frequency radiation with collisional processes in picosecond laser filamentation

When focused in air, ultrashort pulse lasers generate a plasma that produces ultrabroadband radio frequency (RF) radiation via both ponderomotive and plasma wake field current mechanisms. We have performed experiments with high energy pulses and pulse durations up to 5 ps, while holding the power constant. These longer pulses drive much higher electron densities and temperatures, especially as collisional processes become important, and we in turn have measured substantially increased RF generation. We have also developed a Drude numerical model of the ionization within the laser pulse, the heating due to collisions, and the ensuing current density evolution. We find that the low frequency scaling of the simulated current matches the experimental data, which indicates that the ponderomotive currents dominate the RF generation for these atmospheric pressure plasmas. However, the experimentally measured spectra also show an additional low frequency (1–10 GHz) component that grows with laser pulse length, which is consistent with the plasma wake surface wave RF also becoming important as the plasma temperature approaches 100 eV.

Narrow spectra of repeating fast radio bursts: A magnetospheric origin

Fast radio bursts (FRBs) can present a variety of polarization properties and some of them are characterized by narrow spectra. In this work, we study spectral properties from the perspective of intrinsic radiation mechanisms and absorption through the waves propagating in the magnetosphere. The intrinsic radiation mechanisms are considered by invoking quasi-periodic bunch distribution and perturbations on charged bunches moving on curved trajectories. The narrowband emission is likely to reflect some quasi-periodic structure on the bulk of bunches, which may be due to quasi-periodically sparking in a “gap” or quasi-monochromatic Langmuir waves. A sharp spike would appear in the spectrum if the perturbations were to induce a monochromatic oscillation of bunches; however, it is difficult to create a narrow spectrum because the Lorentz factor has large fluctuations, so the spike disappears. Both the bunching mechanism and perturbations scenarios share the same polarization properties, with a uniformly distributed bulk of bunches. We investigated the absorption effects, including Landau damping and curvature self-absorption in the magnetosphere, which are significant at low frequencies. Subluminous O-mode photons cannot escape from the magnetosphere due to the Landau damping, leading to a height-dependent lower frequency cut-off. The spectra can be narrow when the frequency cut-off is close to the characteristic frequency of curvature radiation, however, such conditions cannot always be met. The spectral index is 5/3 at low-frequency bands due to the curvature self-absorption is not as steep as what is seen in observations. The intrinsic radiation mechanisms are more likely to generate the observed narrow spectra of FRBs, rather than the absorption effects.

Stability of the Formation of an Image Using a Terajet with Respect to the Beam Shift

The shift of an image of a dielectric sphere asymmetrically irradiated by a terahertz Gaussian beam in terahertz imaging systems has been demonstrated experimentally. Numerical calculations using the operator scattering theory have shown the bending of the localization region of the electromagnetic field near the shadow surface of the dielectric sphere when it is shifted with respect to the waist center of the Gaussian beam, leading to the formation of the so-called “photonic hook” with the properties depending on the polarization and frequency of the incident radiation. The possibility of reaching a spatial resolution of 0.38λ in the studied range has been shown experimentally. The obtained results can be used to increase the resolution of commercial scanning terahertz systems.

From the experience of the technical examination of hydro-technical tunnels

A comprehensive methodology is proposed and the results of the technical examination of hydraulic tunnels are given. The technique takes into account the influence of water flow, the formation of cavities behind the shell, fixes defects, and reveals the prerequisites for their formation. It consists of visual inspection and non-destructive testing (ultrasonic, electromagnetic, vibro-acoustic). A unified presentation of the examination results is proposed. The optimal basis and operating frequency of the ultrasonic method are substantiated. The gradations of the processes of the formation of cracks in concrete are determined by the frequency of electromagnetic radiation. Examples of tunnel examination are given. Characteristic areas of the objects are identified. For main canals, this is a shell near the entrance and exit portals. Cavities behind the shell can be traced along the entire length of the tunnels. The main defect of the shells of pressure tunnels of power plants is cracks in the reinforced concrete lining. For structures of seasonal drainage, filtration in the bottom is characteristic. The examination results are used to develop projects for repair works. Some methodical regulations can be used for inspecting any underground structures.

Comprehensive Bicubic Formalism of Ordinary and Novel (dm) Particles With Substituted Virtual Novel Electron Describing the Bohr Atom

The particle limiting velocity solutions from the bicubic limiting velocity equation ( Soln, J., 2021.1.2, 2022) have been very useful in carrying out parallel studies of ordinary and novel particles. This study is facilitated with the help of evolutionary congruent parameters, ordinaryz1 ⪯ 1, novel z2 = 1/z1 ⪰ 1 and congruent phase-angle α ⪯ π/2. At smooth matching point z1 = z2 = 1 and α = π/2, there is no physical difference between an ordinary and novel particle as they have the same limiting velocities. At α = π/3 ≺ π/2, they have already different limiting velocities with different other physical characteristics. Ordinary photon γ and novel doubly photon γN are indistinguishable at α = π/2, while at α = π/3 ≺ π/2, they are already physically different. That applies to any other particle, ordinary proton p versus novel proton pN, etc. Through trial and error, one finds that c3 the ordinary particle limiting velocity solution has ratio value of 1 at the comprehensive congruent phase-angle αO = π/5.1 = 0.616 which an ordinary particle of velocity v can satisfy at v ≃ c3, in fact, defining the value of c3. The quantum jump from the ordinary particle comprehensive congruent phase-angle αO to the novel particle comprehensive congruent phase-angle αN = 2αO = 2π/5.1 = 1.232 yields novel particle limiting velocity solution doubly Rc1,3 with ratio value of 1 which a novel particle velocity vN can satisfy with doublyRc1,3 ≃ vN, simply defining the value of doubly Rc1,3. This comprehensive quantum jump with fixed comprehensive congruent phase-angles αO and αN apply to any free and interacting ordinary particle (γ, e, ν,etc.) when connecting to the corresponding free and interacting novel particle (γN, eN, νN, etc.). Concerning the Bohr’s atom, we wish to address the question of negative energy electron e emitting positive energy radiation. To this end we simply substitute e with the virtual novel electron eN with the same radius r and velocity v. This virtual eN, due to the Coulomb potential energy V from the sitting proton p plus the centrifugal force, with the quantized orbital virtual novel electron angular momentum yields the positive virtual novel electron energy in the bicubic formalism. The frequencies of emitted radiation from virtual novel electron is practically the same as from the negative energy electron e.

Machine learning approaches for predicting shielding effectiveness of carbon fiber-reinforced mortars

The exponential growth of communication technologies and the ubiquitous use of electronic devices raise concerns about unintended electromagnetic interference (EMI). Existing research exploring mortars incorporated with carbon fibers for EMI shielding primarily relies on empirical experiments investigating the interplay between shielding effectiveness (SE) and mixed design parameters. This research aims to establish predictive models for SE, focusing on the frequency of radiation and mortar constituents (water-to-cement ratio (W/C), fiber content, sand-to-cement ratio (S/C), and fiber aspect ratio). Employing a diverse array of machine learning algorithms, including stochastic gradient descent (SGD), gradient boosting, random forest, gene expression programming (GEP), AdaBoost, decision tree, K-nearest neighbors, and stepwise linear regression, this study aims to forecast the shielding efficacy of the mortar. Results demonstrate robust model performance, with R2 values and correlation coefficients surpassing 0.85 and 0.95, respectively, across training, testing, and validation datasets. Modeling errors, such as MSE, RMSE, MAE, and MAPE, remain within acceptable bounds for all models. The accuracy of predictions is evidenced by experimental-to-predicted SE ratios falling within the 0.5–1.5 range. Based on available data, parametric investigations conducted using the GEP-derived equation reveal a positive correlation between SE and S/C ratio, aspect ratio, fiber content, and radiation frequency, while indicating an inverse relationship with the W/C ratio. Moreover, employing Shapley additive explanation (SHAP)—a technique grounded in cooperative game theory—enhances the interpretability of SE. In summary, this study provides valuable insights into SE prediction for carbon fiber reinforced cement mortar, underscoring the efficacy of machine learning models in enhancing SE.

Evaluating Peer Review of Palliative Radiation Plans at a Canadian Tertiary Care Cancer Center.

Peer review (PR) of palliative-intent radiation plans is an importantbut understudied component of quality assurance. This retrospective review aims to improve our understanding of palliative PR by examining the characteristics of reviewed plans and peer feedback along with the associated time burden of two different types of PR processes. This single-institution, quality assurance project assessed palliative PR between 2018 and 2020. Initially, the PR involved a multi-disciplinary team PR. Subsequently, it transitioned to independent PR by a single physician. Characteristics of reviewed plans and feedback on PR were captured and abstracted. Time requirements of PR were based on self-reported estimates and attendance records. A total of 1942 cases were reviewed, representing 85.7% (1942/2266) of all palliative-intent plans between 2018 and 2020. A total of41.1% (n=799) were simple (2D/3D) radiation plans while 56.0% (n=1087) were complex (volumetric modulated arc therapy (VMAT) or tomotherapy) plans. Approximately one-third (30.4%, n=590) of all plans were stereotactic treatments. The rate of any peer feedback was 2.3% (n=45), while the rate of a specific recommended or implemented change was 1.2% (n=24) and 0.9% (n=18), respectively. PR before the start of treatment was associated with more frequent recommended (p=0.005) and implemented changes (p=0.008). Most other factors, including plan complexity and use of stereotactic radiation, were not predictive in this analysis. Comparing the independent versus team PR approach, there was no significant difference in recommended or implemented changes. The mean±standard deviation (SD) staff time required per plan reviewed was 36±6 and 37±6 minutes, including 21±6 and 10±6 minutes of physician time, for team and independent PR, respectively. This work highlights the high frequency of complex and stereotactic radiation in the palliative setting, along with the importance of timely PR and the potential benefit of reviewing even simple, 2D/3D radiation plans. Additionally, from a process perspective, our work showed that independent PR may require less dedicated physician time.

Heat transfer in hybrid nanofluid flow between two coaxial cylinders

This study intends to investigate hybrid nanofluid flow between two permeable cylinders in the presence of thermal radiation and heat generation. The numerical solutions are obtained using the finite difference method. The influence of nanoparticle fraction, porous medium, radiation, heat generation, and angular frequency on the velocity, temperature, and Nusselt number are presented using graphs and tables. It was observed that the maximum velocity was attained by TiO2/water nanofluid, whereas the highest temperature distribution is observed in TiO2-Ag/water. Furthermore, the Nusselt number of the fluid increased by 17.5%, 19.7%, and 21.7% when TiO2, TiO2-Ag, and Ag nanoparticles were added to it, respectively.

Magnetization reversal of ferromagnetic nanosample by circularly polarized radiation pulse under resonance condition

We consider the problem of the magnetization dynamics of a nanosized ferromagnetic sample caused by the spin–orbit interaction of electrons arising in the field of an incident electromagnetic wave. We discuss the case when the frequency of the incident electromagnetic radiation is close to the frequency of the interband transitions. We show that with the use of high-power lasers, this mechanism causes the appearance of a magnetization component perpendicular to the initial magnetization of the sample. This component shows oscillations with a frequency lower than that of incident electromagnetic waves. These dynamics make possible the magnetization reversal of the sample.

Improving technology for disinfecting grain from pests of bread stock using ultra-high radiation frequencies

The article is devoted to the study of baking properties of flour made from microwave disinfected grain. The article also discusses methods that can assess the quality and safety of grain products. Measures taken for disinfestation of grain storage facilities are complex, expensive and require a complete shutdown of production, so it is relevant to search for new approaches to disinfestation of grain storage facilities without complete suspension of the work process. In this regard, methods of grain disinfestation using microwave radiation, electric fields and other physical methods that do not require stopping production are of considerable interest. The results of studies have shown that the use of microwave irradiation with high-frequency electromagnetic fields significantly increases the efficiency of destruction of pests in grain. The analysis of the effect of microwave irradiation on moisture, gluten content and temperature of grain indicates that the use of electromagnetic fields with a power of 180 W for 120-160 seconds does not affect the physical and chemical characteristics of grain. According to organoleptic evaluations, at optimal treatment parameters (180 W/m2 for 120-160 seconds) the color, aroma and taste of grain remain unchanged.

Моделирование влияния электромагнитных полей на микросхемы

The article examines the influence of electromagnetic fields on radiation effects in microcircuits, describes the influence of electromagnetic fields depending on the distance from the center of the explosion, and evaluates the degree of protection of microcircuits. Assessments of the impact of electromagnetic fields created by gamma radiation on CMOS microcircuits are considered, the physical process, a mathematical model of the occurrence of leakage current, charge loss, transistor switching speed and electronic mobility are described. The methods of protecting CMOS semiconductors from the effects of electromagnetic fields are considered: shielding, reducing the power and frequency of radiation, and compensation for the effects. Both the physical basis and the mathematical model of the parameters for shielding are considered: attenuation coefficient and shielding efficiency. The main method of protecting microcircuits from electromagnetic fields is determined using shielding, reducing the power and frequency of radiation, as well as compensating for exposure. The article describes the mathematical and algorithmic models on the basis of which a computer model was built to assess the impact of the electromagnetic field on CMOS semiconductors. The assessment of the reliability of the chip security assessment is based on a computer experiment built using a program written in the C# programming language. The result was data from an analysis of protection from the effects of an electromagnetic field on CMOS semiconductors for distances from the epicenter of the explosion at a distance of 10 to 100 km with a step of 10 km.

Effects of high-low frequency electromagnetic radiation on vibrational resonance in Hodgkin–Huxley neuronal system

In this paper, based on the Hodgkin–Huxley (H–H) neuron model, the effects of high-low frequency (HLF) electromagnetic radiation on vibrational resonance (VR) in a single neuron is investigated. It is found that VR can be observed in a single H–H neuron model with or without considering HLF electromagnetic radiation. However, HLF electromagnetic radiation can cause changes in the structure of the resonance peaks and make the maximum region and intensity of the response amplitude smaller, which weakens the VR in the neuronal system. This is because the HLF electromagnetic radiation makes the neuronal electrical activities less regular, resulting in weaker synchronization between input low-frequency signal and output firing. In addition, the effects of the system parameters such as the HF electromagnetic radiation amplitude on the Fourier coefficients are investigated, and it is found that these parameters can also cause changes in the number of resonance peaks, resulting in vibrational mono-resonance and vibrational bi-resonances. When the frequency of the HLF electromagnetic radiation is between 0.014 and 0.041, local anti-resonance can be also observed. This has practical significance in reducing some of the unexpected vibration in aerospace engineering and mechanical fields. The HLF electromagnetic radiation plays an important role in weakening the VR of neuronal systems. Therefore, this study could provide new insights to further control the abnormal electrical activities and information transmission of neurons, which can lead to better design and development of therapeutic programs for neurological disorders and neuroplasticity therapies, and advance neuroscience.

Wavelength measurement of narrowband terahertz radiation using a diffraction grating

We propose a reflective binary amplitude grating-based setup for determining the frequency of narrowband terahertz radiation. Theoretical analysis was conducted on transmissive and reflective configurations utilizing binary and phase gratings. Simulations were performed to determine the parameters of metallic diffraction gratings with millimeter-scale constants, which were produced using laser cutting techniques. Our implementation consists of a cost effective and easy-to-implement setup that operates within the 0.15–1 THz range. The grating is installed on a rotary stage. The experimental results obtained align closely with the theoretical calculations. By understanding the setup parameters and the angle of the 1st diffraction order, we could calculate the frequency of the unknown radiation. The relative error in determining the frequency was less than 2%.

Mobile Tower Radiation and Its Impact on Human Body

In this study, the knowledge of radio frequency radiation emitted by mobile towers and its influence on human health has been offered. Clean environment is one amongst the foremost essentially wants for Human life. Thus that’s what regarding mobile result and its towers pollution and its effect on public health. In investigation of those dangers that may damage us from mobile towers within the way run, was the explanations for putting this on ink research, came this study to seem at the mobile towers and mobile effects Attainable health harm for the aim of diagnosing of these personal effects and to recommend ways in which is accustomed avoid or minimize the risks.

Terahertz phased array antenna based on integrated taper emitters

We report on an all-dielectric integrated taper as a radiating element for terahertz phased array antenna. The taper was manufactured on the base of the silicon substrate and was integrated with effective-medium waveguide. The obtained value of return loss of the taper emitter is 12.9 dB at a radiation frequency of 145.5 GHz. The width of the radiation pattern is 56.2° in the plane of the substrate. To demonstrate the change of the radiation pattern at different values of the phase difference between the elements of the phased array antenna, an appropriate simulation was carried out. It was found that with a phase difference between each pair of adjacent elements of a phased array antenna of 60°, the direction angle of the mainlobe of the radiation pattern changes by 5.5°. A proof of concept experimental demonstration of scanning by the mainlobe of the radiation pattern of a terahertz phased array antenna was carried out. The obtained results open up the possibility of use of the proposed taper emitter in future phased array antennas as part of a new generation communication system with ultra-high data transfer rate.