Short-wave Frequency Research Articles

Short-wave communication link prediction algorithm based on deep learning

In view of the shortcomings that the accuracy of the existing ionospheric models is not enough to reflect the local real-time changes, this paper uses the time series prediction tool of deep learning to obtain the model of a specific communication link, and combines it with the ionospheric theoretical calculation model to improve the accuracy of communication link prediction. The main work is to analyze and compare the international broadcasting data and the model calculation data, summarize and sort out the characteristics of the link data, and then on this basis, look at the change of the difference between the two, and carry out link prediction, which achieves the goal of improving the calculation effect of the link model, which is of great significance to the short-wave frequency management.

Analysis of Influence Factors and Influence Law of Scattering Electric Field of High Voltage Transmission Line in Short Wave Frequency Band

Analysis of Influence Factors and Influence Law of Scattering Electric Field of High Voltage Transmission Line in Short Wave Frequency Band

A Cavity Balun for High-Power Shortwave Transmission

Compared with conventional systems, high power puts forward more requirements on the balun: the materials and structures should be more reliable, able to withstand high power, and have extremely high transmission efficiency. Based on the electromagnetic field theory and the visual optimization method by CST MW Studio, a parallel-connected coaxial cavity balun is proposed in this article that can realize the balance–unbalance conversion in almost the entire shortwave frequency band (4.4–27 MHz). For further improvement of the transmission efficiency and the reduction of voltage standing wave ratio (VSWR), an antenna tuning unit (ATU) was added to the unbalanced port of the cavity, which lowered the VSWR from 1.5 to 1.1. The theoretical value of the breakdown power of the balun is also calculated, and it is much larger than the transmit power. The results of the scaled mode measurement are consistent with the simulation results: the amplitude imbalance of the balanced port is within ±0.5 dB, the phase difference is 180° ± 5°, and the withstand power is at least three times the transmit power, which fully demonstrates that the proposed balun is suitable for high-power shortwave transmitting systems.

On the Radiative Impact of Biomass-Burning Aerosols in the Arctic: The August 2017 Case Study

Boreal fires have increased during the last years and are projected to become more intense and frequent as a consequence of climate change. Wildfires produce a wide range of effects on the Arctic climate and ecosystem, and understanding these effects is crucial for predicting the future evolution of the Arctic region. This study focuses on the impact of the long-range transport of biomass-burning aerosol into the atmosphere and the corresponding radiative perturbation in the shortwave frequency range. As a case study, we investigate an intense biomass-burning (BB) event which took place in summer 2017 in Canada and subsequent northeastward transport of gases and particles in the plume leading to exceptionally high values (0.86) of Aerosol Optical Depth (AOD) at 500 nm measured in northwestern Greenland on 21 August 2017. This work characterizes the BB plume measured at the Thule High Arctic Atmospheric Observatory (THAAO; 76.53∘N, 68.74∘W) in August 2017 by assessing the associated shortwave aerosol direct radiative impact over the THAAO and extending this evaluation over the broader region (60∘N–80∘N, 110∘W–0∘E). The radiative transfer simulations with MODTRAN6.0 estimated an aerosol heating rate of up to 0.5 K/day in the upper aerosol layer (8–12 km). The direct aerosol radiative effect (ARE) vertical profile shows a maximum negative value of −45.4 Wm−2 for a 78∘ solar zenith angle above THAAO at 3 km altitude. A cumulative surface ARE of −127.5 TW is estimated to have occurred on 21 August 2017 over a portion (∼3.1×106 km2) of the considered domain (60∘N–80∘N, 110∘W–0∘E). ARE regional mean daily values over the same portion of the domain vary between −65 and −25 Wm−2. Although this is a limited temporal event, this effect can have significant influence on the Arctic radiative budget, especially in the anticipated scenario of increasing wildfires.

Алгоритми вимірювання частоти кадрової розгортки моніторів для частотно-вибіркового придушення каналів витоку інформації

For a well-known typical model of a leakage signal in the form of a sequence of pixels, horizontal and vertical blank pulses, the differences in frame scanning frequencies for different sizes of monitor screens on rare-crystalline structures and graphics cards of personal computer monitors are considered. The accuracy with which it is necessary to measure the frame rate of the monitor screen in order to form a high-quality noise interference that can muffle the information components of leakage signals through spurious radiation is substantiated. The real spectra of spurious electromagnetic radiation from the screens of monitors on rare-crystalline structures in the short-wave frequency range and the features of measurements of the frequency characteristics of the spectra by Rohde & Schwarz FPH spectrum analyzers are considered. To achieve the required accuracy of measuring the vertical scan frequency, it is proposed to measure the frequencies of harmonics with maximum amplitudes at different frequency sections, and to process the results. Calculation expressions are found for processing the central frequencies of information leakage measured in the areas in order to much more accurately estimate the frame rate of monitors based on rare crystal structures. The sequence of actions for estimating the frame rate of monitors based on rare crystal structures is substantiated. An algorithm of actions has been obtained, which consists in determining the lower and upper values of the numbers of harmonics that correspond to the estimates of the central frequencies, calculating the estimate of the frame frequency and calculating the accuracy of the estimate. If the calculated accuracy estimate is less than the previously justified one, a conclusion is made about a satisfactory measurement of the frame frequency. If necessary, to obtain more accurate results, increase the number of studied frequency sections. The practical use of the obtained expressions for data processing at thirty-two frequency sections is considered, and conclusions are drawn about satisfactory results in terms of the accuracy of measuring the frame frequency when using the usual spectrum analyzer measurement mode.

Using Physical Factor Therapy for Postoperative Patients with Cerebral Apoplexy Voiding Dysfunction: A Case Study

Objective: We introduce and analyze by physical factors treatment case the method and effect of urinary retention after stroke, li xx hospital diagnosis: patients with cerebral hemorrhage postoperative recovery, on the left side of the limb dysfunction, urinary bladder sensitivity is poorer, lack of detrusor activity, urethral sphincter muscle tension increased, urination disorders, urinary retention. Treatment methods: Using electrical therapeutic apparatus, electrodes cross placed in the lower abdomen in patients with bladder section. Using percutaneous nerve electrical stimulation, placed therapeutic apparatus is the cathode respectively in patients with the third sacral vertebral and bladder reflex zone, set the treatment frequency is 120 hz, voltage range of 20 ~ 26 v. Using shortwave treatment, set the short-wave frequency therapy apparatus 10 w, before and after the placement of electrodes, to help urethral sphincter muscle tension relaxed, eliminate urinary tract inflammation and edema. Results: By interfering with the treatment, percutaneous neuromuscular electrical stimulation (TENS) and short wave 15 days after treatment, patients can feel obviously can urinate and pa ontaneously 300 ml urine volume. Conclusion: interference electric treatment can stimulate the detrusor contraction, short-wave can improve urethral sphincter muscle tension, Percutaneous neuromuscular electrical stimulation therapy can excitement parasympathetic promote bladder function, improve urinary retention in patients with quality of life.

Bound and free infragravity wave energy over a bar

The propagation of bound and free infragravity wave energy under short-wave breaking conditions induced by a longshore bar is investigated through field observations. Near-bottom pressure records deployed in a cross-shore array at S. Jacinto barred beach (Portugal) were analysed. In these observations, short-wave breaking induced by the longshore bar occurred mainly in intermediate water depths.The ratio between bound and total (bound plus free) infragravity wave energy was estimated with the methodology of Herbers et al. (1994). This ratio had a maximum value of 0.6 at the breaking onset, which is consistent with values presented elsewhere.A decrease of the bound infragravity wave energy was observed after short-wave breaking near the bar crest. This is in part due to nonlinear energy transfers from infragravity to short-wave frequencies as detected on the imaginary part of the bispectrum, in a weakly dispersive Boussinesq approximation. The other part is due to the process of release/transform bound into free infragravity wave energy that was assessed with a simplified energy balance equation.A conceptual model for the exchange of bound infragravity wave energy during short-wave breaking in intermediate water depths is proposed. This conceptual model involves both the kh and the ga/C2 generalized nonlinearity parameter.

Between Public and Private, Britain and Canada: Newfoundland Radio 1934-1949

This article examines Newfoundland radio during the period when Newfoundland was governed by a British-appointed Commission of Government (1934–1949), devoting particular attention to the political sensitivities and implications involved when one nation essentially assumed control of radio broadcasting in one of its dominions. The BBC had played the role of midwife in bringing the Broadcasting Corporation of Newfoundland into being during the 1930s, and provided regular advice to the Commission of Government, at a time when the countries of the empire were encouraged to follow the Corporation’s public service organisation as a model. The relationship between the BBC and the BCN did come to sour, however, due to a feeling in St. John’s that the larger Corporation was neglecting its tiny counterpart. As will be demonstrated using archival sources, there was some justification for this. Due to the particular constitutional status of Newfoundland, as in effect a Dependency of the United Kingdom, the BBC did not treat it on a par with the self-governing Dominions, which meant that possibilities for exchange were limited or non-existent. As well as examining these political issues, the article will develop a portrait of the unique aspects of Newfoundland’s early radio culture. Newfoundland is a particularly appropriate case study for radio beyond boundaries as, due to its geographical location, listeners have traditionally been exposed to US and Canadian radio stations as well as domestic broadcasters and short-wave frequencies. Furthermore, conventional boundaries between public and private models of broadcasting do not apply in Newfoundland, where commercial radio programming has often performed a valuable public service function.

Spatial and temporal distributions of turbulence under bichromatic breaking waves

The present study aims to extend insights of surf zone turbulence dynamics to wave groups. In a large-scale wave flume, bichromatic wave groups were produced with 31.5 s group period, 4.2 s mean wave period, and a 0.58 m maximum wave height near the paddle. This condition resulted in plunging-type wave breaking over a fixed, gravel-bed, barred profile. Optic, acoustic and electromagnetic instruments were used to measure the flow and the spatial and temporal distributions of turbulent kinetic energy (TKE). The measurements showed that turbulence in the shoaling region is primarily bed-generated and decays almost fully within one wave cycle, leading to TKE variations at the short wave frequency. The wave breaking-generated turbulence, in contrast, decays over multiple wave cycles, leading to a gradual increase and decay of TKE during a wave group cycle. In the wave breaking region, TKE dynamics are driven by the production and subsequent downward transport of turbulence under the successive breaking waves in the group. Consequently, the maximum near-bed TKE in the breaking region can lag the highest breaking wave by up to 2.5 wave cycles. The net cross-shore transport of TKE is in the shoaling region primarily driven by short-wave velocities and is shoreward-directed; in the wave breaking region, the TKE transport is seaward-directed by the undertow and the long-wave velocities. Downward transport of TKE is driven by the vertical component of the time-averaged flow. The cross-shore and vertical diffusive transport rates are small relative to the advective transport rates.

Research on Anti-Jamming Performance of GMSK in Shortwave Frequency Hopping

In this paper, we first analyze the performance of GMSK against partial-band interference in short-wave and slow-frequency hopping. Numerical simulation results show that when the value is different, the BER of the BER varies with the SIR. When is small, the BER of SFH/GMSK is smaller than that of SFH/MFSK under the same conditions. When is large, the BER of SFH/GMSK is smaller than that of SFH/BFSK, but larger than the BER of SFH/4FSK. Then we analyze the anti-multipath interference performance of GMSK in short-wave slow frequency hopping, and choose Rayleigh fading channel and Rice fading channel for simulation. The flat fading and frequency selective fading are used in Rayleigh fading channel respectively. The simulation results show that in Rayleigh multi-path fading channel, SFH/GMSK anti-multipath fading performance is better than SFH/MFSK; in Rician channel, the larger the K value is, the smaller the error rate is. Finally, three kinds of diversity combining methods are added to a frequency-selective fading SFH/GMSK short-wave channel system. The simulation results show that compared with the bit error rate of multipath channels, by combining multipaths the system performance of bit error rate can get 2dB improvement.

Infragravity wave energy changes on a dissipative barred beach: A numerical study

The influence of bars on the infragravity wave energy changes in dissipative beaches is analysed through numerical simulations of random wave propagation. The analysis of the simulated data includes the cross-shore evolution of the significant short and infragravity wave heights, the phase-lag between the radiation stress and the infragravity wave oscillations and the balance between the infragravity wave energy flux gradient and the rate of work done by the radiation stress. These simulated data were subjected to a sensitivity analyses aiming to assess the influence of the water depths over the bar crest and of the JONSWAP peak-enhancement factor.The presence of a bar induces partial short wave dissipation through depth-induced breaking. Over the bar, the infragravity wave energy flux gradient is almost balanced by the work done by the radiation stress for the analysed range of water depths and JONSWAP peak-enhancement factors.Nonlinear energy transfers between short and infragravity wave frequencies are therefore the most important physical process to explain the infragravity wave energy changes that occur over a dissipative bar. For the shallowest test case, infragravity wave dissipation, probably induced by depth-induced breaking, can play a role on the downward slope of the bar. The water depth over the bar crest controls the infragravity wave energy changes that occur between the bar crest and the shoreline.A transition range associated to Ursell numbers between 0.3 and 1 separates two clusters associated to nonlinear energy transfers. For Ursell numbers below this range, nonlinear energy transfers occur from the short to the infragravity wave frequencies. In contrast, for Ursell numbers above this limit they occur from infragravity to the short wave frequencies. A parametrization widely used in operational wave models performs satisfactory for Ursell numbers between 0.1 and 1 over the simulated dissipative barred beach profiles.

Swash saturation: an assessment of available models

An extensive previously published (Hughes et al. Mar Geol 355, 88–97, 2014) field data set representing the full range of micro-tidal beach states (reflective, intermediate and dissipative) is used to investigate swash saturation. Two models that predict the behavior of saturated swash are tested: one driven by standing waves and the other driven by bores. Despite being based on entirely different premises, they predict similar trends in the limiting (saturated) swash height with respect to dependency on frequency and beach gradient. For a given frequency and beach gradient, however, the bore-driven model predicts a larger saturated swash height by a factor 2.5. Both models broadly predict the general behavior of swash saturation evident in the data, but neither model is accurate in detail. While swash saturation in the short-wave frequency band is common on some beach types, it does not always occur across all beach types. Further work is required on wave reflection/breaking and the role of wave-wave and wave-swash interactions to determine limiting swash heights on natural beaches.

High-power shortwave DRM transmitter in solid-state technology

ABSTRACTDesign of high-power shortwave broadcast transmitters is one among the rare areas in the field of radiofrequency (RF) electronics, where the electron tube, as the main element for amplification of RF signal, is still in active use. The first successful attempts to replace the electron tube with solid-state components, primarily in the output stage amplifier modules for the Digital Radio Mondiale (DRM) shortwave broadcast transmitters have been published only recently. With the latest technology advancements in RF power transistors, it is now possible for commercially available RF power MOSFET transistors to be used for switching purposes at shortwave frequencies. Here, an architecture of a 10 kW shortwave broadcast transmitter with solid-state power amplifier modules in the RF output stage is proposed. Different implementations of the RF output stage that include power adding network from each amplifier module and the output matching network are analysed, both analytically and numerically. After choosing the optimal architecture, a prototype of a commercial shortwave DRM broadcast transmitter was designed and constructed, measured, tuned and tested at RIZ Transmitter factory Zagreb.

Skin thermophysiological effects of 448 kHz capacitive resistive monopolar radiofrequency in healthy adults: A randomised crossover study and comparison with pulsed shortwave therapy

ABSTRACTRadiofrequency-based electrophysical agents (EPA) have been used in therapy practice over several decades (e.g., shortwave therapies). Currently, there is insufficient evidence supporting such devices operating below shortwave frequencies. This laboratory-based study investigated the skin physiological effects of 448 kHz capacitive resistive monopolar radiofrequency (CRMRF) and compared them to pulsed shortwave therapy (PSWT). In a randomised crossover study, seventeen healthy volunteers received four treatment conditions – High, Low and Placebo dose conditions receiving 15-min CRMRF treatment and a Control condition receiving no intervention. Fifteen participants also received high dose PSWT for comparison. Treatment was applied to the right lower medial thigh. Pre, post and 20-min follow-up measurements of skin temperature (SKT), skin blood flow (SBF) and nerve conduction velocity (NCV) were obtained using Biopac MP150 system. Group data were compared using the ANOVA model. Statistical significance was set at p ≤ 0.05 (0.8P, 95%CI). Significant increase and sustenance of SKT with both high and low dose CRMRF was demonstrated over the other groups (p < 0.001). PSWT increased SKT significantly (p < 0.001) but failed to sustain it over the follow-up. However, among the five conditions, only high dose CRMRF significantly increased and sustained SBF (p < 0.001). Overall, the CRMRF physiological responses were significantly more pronounced than that of PSWT. No significant changes in NCV were noted for any condition. Physiological changes associated with CRMRF were more pronounced when compared to PSWT, placebo or control. Any potential stronger therapeutic benefits of CRMRF need to be confirmed by comparative clinical studies.

Analysis on the Influence of Transmission Lines span on Passive Interference in Shortwave

The passive interference of transmission lines to nearby radio stations may affect the effective reception and transmission of radio station signals. Therefore, the accurate calculation of the electromagnetic scattering of transmission lines under the condition of external electromagnetic waves is the basis for determining the reasonable avoidance spacing of the two. For passive stations operating in short-wave frequencies, passive interference is mainly generated by the tower, and span is one of the most significant factors affecting passive interference. This paper uses the method of moments to carry out the passive interference calculations under normal circumstances, expounds the method of calculating the electromagnetic field of transmission line at the same time. And elaborates the method for calculating the electromagnetic field of the transmission line, obtains the space electric field intensity of the transmission line at the same working frequency and space location of the plane wave. Applying the approximate formula to calculate the formula for the span and critical distance between the observation point and the transmission line.

Analysis on the Influence of the Height of Tower on Passive Interference in shortwave

The passive interference of transmission lines to nearby radio stations may affect the effective reception and transmission of radio station signals. Therefore, the accurate calculation of the electromagnetic scattering of transmission lines under the condition of external electromagnetic waves is the basis for determining the reasonable avoidance spacing of the two. For passive stations operating in short-wave frequencies, passive interference is mainly generated by the tower. This paper uses the method of moments to perform passive interference calculations under normal circumstances, And elaborates the method for calculating the electromagnetic field of the transmission line, obtains the space electric field intensity of the transmission line at the same working frequency and space location of the plane wave. Uses the approximate formula to inductive the formula for calculating height of tower and the protective distance.

Leading-order nonlocal kinetic energy in peridynamics for consistent energetics and wave dispersion

This work considers the approximation of peridynamics by strain-gradient models in the linear, one-dimensional setting. Strain-gradient expansions that approximate the peridynamic dispersion relation using Taylor series are compared to strain-gradient models that approximate the peridynamic elastic energy. The dynamic and energetic expansions differ from each other, and neither captures an important feature of peridynamics that mimics atomic-scale dynamics, namely that the frequency of short waves is bounded and non-zero.The paper next examines peridynamics as the limit model along a sequence of strain-gradient models that consistently approximate both the energetics and the dispersion properties of peridynamics. Formally examining the limit suggests that the inertial term in the dynamical equation of peridynamics – or equivalently, the peridynamic kinetic energy – is necessarily nonlocal in space to balance the spatial nonlocality in the elastic energy. The nonlocality in the kinetic energy is of leading-order in the following sense: classical elasticity is the zeroth-order theory in both the kinetically nonlocal peridynamics and the classical peridynamics, but once nonlocality in the elastic energy is introduced, it must be balanced by nonlocality in the kinetic energy at the same order. In that sense, the kinetic nonlocality is not a higher-order correction; rather, the kinetic nonlocality is essential for consistent energetics and dynamics even in the simplest setting. The paper then examines the implications of kinetically nonlocal peridynamics in the context of stationary and propagating discontinuities of the kinematic fields.

Continuous-mode 448 kHz capacitive resistive monopolar radiofrequency induces greater deep blood flow changes compared to pulsed mode shortwave: a crossover study in healthy adults

Aims: Radiofrequency-based electrophysical agents (EPAs) have been used in therapy practice over several decades (e.g. shortwave therapies). Currently, there is insufficient evidence supporting such EPAs operating below shortwave frequencies. This laboratory-based study investigated the deep physiological effects of 448 kHz capacitive resistive monopolar radiofrequency (CRMRF) and compared them to pulsed shortwave therapy (PSWT).Methods: In a randomized crossover study, 17 healthy volunteers initially received four treatment conditions: high, low and placebo dose conditions receiving 15-min CRMRF treatment and a control condition receiving no intervention. Fifteen participants additionally received high-dose PSWT as fifth condition, for comparison. Pre- and post-treatment measurements of deep blood flow and tissue extensibility were obtained using Doppler ultrasound and sonoelastography. Group data were compared using analysis of variance model. Statistical significance was set at p ≤ .05, 0.8 power, and 95% confidence interval.Results: Significant increases in volume and intensity of deep blood flow were obtained with CRMRF over placebo, control (p = .003) and PSWT (p < .001). No significant changes in blood flow velocity or tissue extensibility were noted for any condition.Conclusions: Deep blood flow changes with CRMRF were more pronounced than that with PSWT, placebo or control. Potential greater therapeutic benefits need to be confirmed with comparative clinical studies.

Numerical model for zonal flow generation by magnetized Rossby waves in the ionosphere with the background shear flow

A theoretical-numerical description of zonal flow generation in the turbulent ionosphere by controlled inhomogeneous background wind is given. The generalized Charney–Obukhov equation, which describes the nonlinear interaction of five different-scale modes (primary modes, relatively short-wave ultra-low frequency (ULF) magnetized Rossby waves (MRWs) (pumping waves), two satellites of these MRWs, long-wave zonal mode, and large-scale background shear flows (inhomogeneous wind)) is used. New features of energy transfer from relatively small-scale waves and the background shear flow into that of largescale zonal flows and nonlinear self-organization of the five-wave collective activity in the ionospheric medium are identified based on the numerical solution of the corresponding system of equations for perturbation amplitudes (generalized eigenvalue problems). It is shown that if there is the background shear flow with a moderate amplitude growth the modulation instability increment and intensifies the zonal flow generation, while a very strong shear flow significantly reduces the modulation instability increment and can even suppress the generation process.

DRM Reception Results in Long-Range Short Wave Broadcasting

The Digital Radio Mondiale (DRM) digital radio standard is the only one recommended by the ITU to be used in Short Wave bands. These bands present unique characteristics for the broadcasting, very big coverage areas and long-range transmission. But they suffer of complicated propagation channel with big time variations that make difficult the regular broadcasting operation. In order to evaluate the DRM performance, field trials were made in Brazil by the Brazilian Government. The objective was to evaluate DRM technology for long-range transmission in Short Wave frequencies. In this paper, the results of these field trials are explained. Two frequencies were used during a period of three weeks at different hours of the day. The transmission was made from French Guyana and the reception was tested in Brasilia.