Impact of atmospheric ionization by delayed radiation from highaltitude nuclear explosions on radio communication

In this study,we investigated the motion,shape,and delayed radiation intensity of a radioactive cloud by establishing a volume-source model of delayed radiation after high-altitude nuclear explosions.Then,the spatial distribution of electron number density at different moments on the north side of the explosion point generated by delayed γ-rays and delayed β-rays from the radioactive cloud under the influence of the geomagnetic field was calculated by solving chemical reaction kinetics equations.The impact of radio communication in the different frequency bands on the process of atmospheric ionization was also studied.The numerical results of the high-altitude nuclear explosion (120 km high and with a 1 megaton equivalent at 40°N latitude) indicated that the peak of electron number density ionized delayed γ-rays is located at a height of approximately 100 km and that of electron number density ionized delayed β-rays is about 90 km high.After 1 min of explosion,the radio communication in the medium frequency (MF) and high-frequency (HF)bands was completely interrupted,and the energy attenuation of the radio wave in the very high-frequency (VHF)band was extremely high.Five minutes later,the VHF radio communication was basically restored,but the energy attenuation in the HF band was still high.After 30 min,theVHF radio communication returned to normal,but its influence on the HF and MF radio communication continued.

The Influence of the Sun and Moon on the Observation of Very High Energy Gamma-ray Sources Using EAS Arrays

With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.

Simulation and Performance Analysis of Six Types of Sun Tracker Approaches:A Comparative Analysis for Solar Concentrating Technology Application at Burkina Faso

Modelization equations of six approaches for tracking the sun are recalled and used to evaluate the constraints and performances to which they lead to.The geographical study case is taken for the specific latitude of 12 North that is a good matching with the location of the country of Burkina Faso.Three decisive periods were locally established in order to consider the different travels of the sun on sky during one year.This work presents some technical data which facilitates the choice of sun tracking approaches with concern of a concentrator limits such as its angle of acceptance,its motion control card interpolation model,or its minimum irradiation level for energy conversion effectiveness.

Knowledge and Practices of Health Professionals on the Optimization of Radiation Protection in Diagnostic Radiology in Children and Adults in the General Referral Hospitals of Bukavu in South Kivu, DRC

The aim of this research was to assess the knowledge and practices of radiological versus non-radiological health professionals on the optimisation of radiation protection in paediatric and adult radiology in BUKAVU hospitals. To achieve this, we surveyed a convenience sample of 73 health professionals including 23 radiologists working in the hospitals surveyed to assess knowledge and level of implementation of radiation protection principles. Also, physical parameters were taken for the calculation of entry doses in paediatric and adult radiology units for comparison with the International Commission on Radiological Protection (ICRP) diagnostic reference levels. After analysis of the data, the following was found: although radiologists have sufficient knowledge of radiation protection standards, technical constraints do not allow them to observe the dose limitation principle recommended by the ICRP. This is why several radiology departments, including those of the HPGRB, the MWANZI clinic and CIRIRI hospital, have proved to be very irradiating for children. However, radiologists and non-radiologists alike do not contribute positively to the optimisation of radiation protection in the diagnostic use of X-rays. Therefore, support in the implementation of radiation protection principles and regular monitoring of the units as well as replacement of non-standard equipment is necessary to promote patient and environmental safety by optimising radiation protection.

Non-uniform temperature distribution of the main reflector of a large radio telescope under solar radiation

The non-uniform temperature distribution of the main reflector of a large radio telescope may cause serious deformation of the main reflector,which will dramatically reduce the aperture efficiency of a radio telescope.To study the non-uniform temperature field of the main reflector of a large radio telescope,numerical calculations including thermal environment factors,the coefficients on convection and radiation,and the shadow boundary of the main reflector are first discussed.In addition,the shadow coverage and the non-uniform temperature field of the main reflector of a 70-m radio telescope under solar radiation are simulated by finite element analysis.The simulation results show that the temperature distribution of the main reflector under solar radiation is very uneven,and the maximum of the root mean square temperature is 12.3℃.To verify the simulation results,an optical camera and a thermal imaging camera are used to measure the shadow coverage and the non-uniform temperature distribution of the main reflector on a clear day.At the same time,some temperature sensors are used to measure the temperature at some points close to the main reflector on the backup structure.It has been verified that the simulation and measurement results of the shadow coverage on the main reflector are in good agreement,and the cosine similarity between the simulation and the measurement is above 90%.Despite the inevitable thermal imaging errors caused by large viewing angles,the simulated temperature field is similar to the measured temperature distribution of the main reflector to a large extent.The temperature trend measured at the test points on the backup structure close to the main reflector without direct solar radiation is consistent with the simulated temperature trend of the corresponding points on the main reflector with the solar radiation.It is credible to calculate the temperature field of the main reflector through the finite element method.This work can provide valuable references for studying the thermal deformation and the surface accuracy of the main reflector of a large radio telescope.

The Science of Radio Astronomy: An Investigation of Crab Nebula

The science of radio astronomy focuses on the observation and study of celestial objects by reading their radio waves. The 5 meter radio-telescope is able to observe different radio sources using a C-band LNB. This research was essentially focused on Crab Nebula, also known as Taurus A. The study led to interesting observations, which were validated numerically using various scientific computing software. The radio waves emitted by Taurus A are readable by the RTL-SDR, a software defined radio receiver. This device is capable of reading radio frequencies in the range of 0.5 MHZ to 1700 MHZ.

Radiation pattern analyses of circular aperture antenna to generate radio orbital angular momentum

圆形口径天线近来被认为是在毫米波频段产生具有高功率电磁轨道角动量的自然方式之一。但是,目前的研究并没有给出该种天线的辐射特性分析。本文从理论角度推导了产生轨道角动量的圆形口径天线的辐射特性,并通过仿真实验验证了理论结果的准确性。正交横电模(TE)和横磁模(TM)激励的圆形口径天线的仿真实验表明,TE_(g1)可以产生纯净g–1模态的轨道角动量,更适合在实际应用中使用。本文对该类天线的分析有助于毫米波电磁波涡旋的产生的研究和分析。

The Gyrosynchrotron Radiation Spectrum in a Nonuniform Source

Effects of the energy spectral index δ, low energy cutoff E0 and number density N of energetic electrons on gyrosynchrotron spectrum are investigated for a model source with a nonuniform magnetic field. It is found that the flux density SVT of the x-mode and o-mode systematically increase with increasing E0, N and with decreasing δ. The peak frequency of the spectrum, vp, also systematically increases as increasing E0 and N, but it may not depend on δ. The gyrosynchrotron radiation in the nonuniform case is polarized predominately in the x-mode at v ≥ 3 GHz. A sense reversal of circular polarization also occurs but at much lower frequencies （v ≤ 3 GHz）. The reversal frequency also increases with increasing E0 and N, but it perhaps is independent of δ.

Tuning control system of a third harmonic superconducting cavity in the Shanghai Synchrotron Radiation Facility

Beam lifetime is dominated by Touschek scattering at the Shanghai Synchrotron Radiation Facility(SSRF).Touschek loss rate is affected by probability for scattering beyond the RF acceptance and the volume charge density of the bench.In the phaseⅡupgrade of the SSRF,a third harmonic superconducting cavity will be used to enhance the Touschek lifetime by lengthening the bunches.The Touschek lifetime improvement factor is affected by the voltage of a harmonic cavity.To stabilize the cavity voltage,a tuning control system was designed to control it.The design of the tuning control system was based on the SSRF third-generation low-level RF control system.Some hardware and specialized algorithms were redesigned to fit the harmonic cavity control.The design of the tuning control system is complete,and the control system has been tested.The test result shows that the fluctuation of amplitude is<±0.34%within 1.5 h,which satisfies the stability requirement.

Self-adapting radiation control method for RFS in tracking

The aim of this paper is to achieve the radio frequency stealth(RFS) during the course of tracking by controlling the radiation energy and the interval of a radar. Firstly, we build the model of probability of interception with the once radiation during the course of tracking. Secondly, we establish the model of the cumulative probability of interception to describe the effect of RFS throughout the tracking process and obtain two solutions that are minimizing the probability of interception and the radiation times to reduce the cumulative probability of interception. Thirdly, we propose a self-adapting radiation energy control method(SARE)to minimize the probability of interception. Fourthly, we propose a self-adapting radiation interval control method(SARI) to minimize radiation times. Fifthly, combining SARE with SARI, we propose a SARE-SARI control method(SAEI) during the course of tracking.Finally, we compare SAEI with two others by simulation, and the results show the effect of RFS of SAEI is better than the other two,but we have to make a trade-off between the ability of RFS and the effect of tracking.

Ground-based Observations of Ultraviolet and Total Solar Radiation in Shenyang,Northeast China

Objective This work explores the diurnal variation of Solar ultraviolet radiation （UVR） and total solar radiation （TSR） in northeast China,using daily observations of UVR and TSR in Shenyang.Methods UVR and TSR measurements were carried out from March 1st,2006 to December 31st,2009 in Shenyang,Liaoning province,China （41°51＇ N,123°27＇ E）.Results Both TSR and UVR showed seasonal variation,reaching the highest levels in summer and the lowest in winter.They showed the greatest fluctuation in summer and autumn.The irradiance of TSR and UVR on clear days around the equinoxes and solstices increased substantially compared with the mean seasonal irradiance,especially in autumn.The whole day accumulated dose of UVR in winter was far less than that during the middle part of a summer day （i.e.between 10：00 and 14：00）.It was also less than the accumulated summer dose of morning and afternoon （i.e.between 8：00 and 10：00 and 14：00 and 16：00）.Conclusion The instant irradiance and daily accumulated amount of UVR are low in Shenyang,especially in autumn and winter.Thus concern about the health effects arising because shortage of UVR in northeast China is warranted.

A Primary Study of the Variations of Vertical Radiation with the Beijing 325-m Meteorological Tower

The Beijing 325-m Meteorological Tower (325MT) is used to observe the vertical variation of solar radiation. Results of the experiments indicate that the automatic radiation monitoring system, including a sun tracker and data collection system, works well and all the specifications meet WMO observation standards. The measurement data show that there is a significant radiation decrease from 320 m to the surface, where the difference is only about 30 W m-2 on light air-pollution days, while the maximum reaches about 110 W m-2 when heavy pollution appears near the ground. The global UV radiation decreases on heavy air-pollution days and under poor visibility conditions, and the difference between 300 m and 8 m is larger than on clear days.

Study of Solar Radiation in View of Photovoltaic Systems Optimization

The meteorological data concerning solar radiation are generally not sufficient to allow quantifying all the phenomena which occur when a photovoltaic panel receives solar light. It is therefore, necessary to supplement these data by using astronomical calculation for the sun position and modelling the atmosphere. A simple method to calculate global, diffuse and direct irradiance on vertical and tilted surfaces for all uniform sky conditions (clear sky and overcast sky), developed in Constantine (Algeria) and Louvain-la-neuve (Belgium), has been compared with experimental data obtained at Ghardaia (Algeria). In spite of its simplicity, the method furnishes reasonably good predictions, in comparison with experimental data, and can be proposed as a simpli?ed tool for design purposes. This method relies on the fact that we can calculate the irradiance on a plane with arbitrary orientation and inclination, based on the measurement of a single irradiance value on a reference plane.

Characteristics of terahertz coherent transition radiation generated from picosecond ultrashort electron bunches

This paper presents a method of generating terahertz （THz） coherent transition radiation （CTR） from picosecond ultrashort electron bunches including single and train bunches, which are produced by a photocathode radio frequency gun. The radiation characteristics of THz CTR including formation factor and energy spectrum are analysed in detail. With the help of a 2-dimensional particle-in-cell simulation, the radiation characteristics including power, energy and magnetic field are analysed. The results show that the radiation frequency can be adjusted by tuning the repetition frequency of the train bunch and the energy can be enhanced with the train bunches.

DSC based Dual-Resunet for radio frequency interference identification

Radio frequency interference(RFI)will pollute the weak astronomical signals received by radio telescopes,which in return will seriously affect the time-domain astronomical observation and research.In this paper,we use a deep learning method to identify RFI in frequency spectrum data,and propose a neural network based on Unet that combines the principles of depthwise separable convolution and residual,named DSC Based Dual-Resunet.Compared with the existing Unet network,DSC Based Dual-Resunet performs better in terms of accuracy,F1 score,and MIoU,and is also better in terms of computation cost where the model size and parameter amount are 12.5%of Unet and the amount of computation is 38%of Unet.The experimental results show that the proposed network is a high-performance and lightweight network,and it is hopeful to be applied to RFI identification of radio telescopes on a large scale.

Harmonic Structures of Gyrosynchrotron Radiation and Cyclotron Maser Instability

The harmonic structures of the gyrosynchrotron radiation are studied and compared with the results of the electron cyclotron maser instability. The structures only appear at lower harmonics (s < 10), and their peaks deviate by a small amount from integer harmonic numbers. The amplitudes of harmonic structures of the extraordinary modes are usually larger than that of the ordinary modes. The numbers and amplitudes of harmonic structures increase with increasing electron energy spectral index δand propagation angle θ.All the properties of harmonic structures are consistent with the predictions of the electron cyclotron maser instability in an extremely magnetized plasma on the basis of Maxwell and Vlasov equations. The physical relations between gyrosynchrotron radiation and cyclotron maser instability and a possible application of the properties of the harmonic structures are discussed.

Investigation on the Formation of Herringbone Structure in TypeⅡSolar Radio Bursts

We report detailed observation of the“herringbone”of a Type II solar radio burst that occurred on 2010 November 3rd.Data from the Space Weather Prediction Center,National Oceanic and Atmospheric Administration,e-CALLISTO,and Nan?ay Radio Heliograph are analyzed.We determine the brightness temperature and degree of circular polarization of the“herringbone”burst.Correlations between the physical parameters and the“herringbone”are examined.Based on the relationship,this is the first study that suggested this“herringbone”was generated through fundamental plasma.

Estimation of Solar Observations with the Five-hundred-meter Aperture Spherical Radio Telescope(FAST)

We present the estimation of solar observation with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).For both the quiet Sun and the Sun with radio bursts,when pointing directly to the Sun,the total power received by FAST would be out of the safe operational range of the signal chain,even resulting in damage to the receiver.As a conclusion,the Sun should be kept at least~2°away from the main beam during observations at~1.25 GHz.The separation for lower frequency should be larger.For simplicity,the angular separation between the FAST beam and the Sun is suggested to be~5°for observations at 200 MHz or higher bands.

Electromagnetic Radiation Causes Weight Loss and Weight Destabilization of Objects with Presumed Elevated Levels of KELEA (Kinetic Energy Limiting Electrostatic Attraction), Relevance to Human Health and to Global Warming

A natural force has been proposed, which is required to prevent the fusion and disappearance of the discrete electrical charges that are present on electrostatically attached opposing electrical charges. This force may also explain the repulsion between objects with either matching positive or negative electrical charges. The energy of this force is referred to as KELEA (kinetic energy limiting electrostatic attraction). KELEA is especially attracted to dipolar compounds and to other materials with spatially separated opposite electrical charges. These compounds can be used to increase the level of KELEA in water. KELEA activated water can become an added source of KELEA for objects that are placed in close proximity to the water. It is generally held that the weight of an object is solely determined by its mass in relation to that of the earth. Yet, it was previously reported that the measured weight of certain KELEA attracting objects can undergo considerable variability over time. This observation is consistent with the concept that KELEA can contribute to the measured weight of certain objects. The present study strengthens this concept by demonstrating that the weight of cellulose containing materials, including paper, cotton fabrics, and wood, is increased if the materials are placed close to containers of KELEA activated water. It is further shown that electromagnetic radiation can significantly reduce the added weight of the KELEA exposed cellulose containing materials. Moreover, the previously added weight of the materials can be regained by replacing the materials back into the KELEA enhanced environment. It is proposed that the electrical charges that accompany electromagnetic radiation are able to competitively withdraw some of the KELEA from certain KELEA-enhanced objects. This effect can be reliably demonstrated using single sheets of writing paper, which are primarily composed of mechanically-bonded, branched cellulose fibers. There can be considerable fluctuations of the weight of the materials exposed to electromagnetic radiation after having been placed nearby to KELEA activated water. The weight instability is interpreted as being due to the electromagnetic radiation also triggering a dynamic process of rapid additions and removals of significant quantities of KELEA to and from objects. These observations are relevant to the further understanding of KELEA and to the potential health and climate consequences of manmade electromagnetic radiation causing a reduction in the environmental levels of KELEA.