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Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts 1 – 3 . Recent observations of a Galactic FRB 4 – 8 suggest that at least some FRBs originate from magnetars, but the origin of cosmological FRBs is still not settled. Here we report the detection of 1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref.  9 ). These observations show irregular short-time variation of the Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit ( au ; Earth–Sun distance) of the source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy 10 – 12 show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova. Analysis of a set of 1,863 bursts from the repeating source FRB 20201124A provides evidence of a complicated magnetized site within about an astronomical unit from the source in a barred galaxy.

Fast radio bursts (FRBs) are millisecond-duration radio transients 1 , 2 of unknown origin. Two possible mechanisms that could generate extremely coherent emission from FRBs invoke neutron star magnetospheres 3 – 5 or relativistic shocks far from the central energy source 6 – 8 . Detailed polarization observations may help us to understand the emission mechanism. However, the available FRB polarization data have been perplexing, because they show a host of polarimetric properties, including either a constant polarization angle during each burst for some repeaters 9 , 10 or variable polarization angles in some other apparently one-off events 11 , 12 . Here we report observations of 15 bursts from FRB 180301 and find various polarization angle swings in seven of them. The diversity of the polarization angle features of these bursts is consistent with a magnetospheric origin of the radio emission, and disfavours the radiation models invoking relativistic shocks. Polarization observations of the fast radio burst FRB 180301 with the FAST radio telescope show diverse polarization angle swings, consistent with a magnetospheric origin of the emission.

In recent years, meta-materials received wide attention for its negative refractive index in microwave system. Many papers have reported the theoretical and experience development of meta-materials. The main work of this paper includes fabrication of the samples and measuring the property. We design the parameters of the structure and then using tape-casting technique to fabricate periodic silver structure in the ceramic substrate. The measurement fixture is designed, and HP8720ES vector network analyzer is used to measure the spectra and the field distribution of samples. At about 12 GHz, samples had an obvious photonic band gap from S 21 parameter measure results. By the field distribution in the two dimension plane of samples, we obtained the abnormal refraction phenomenon which can audio–visual validate the existence of meta-materials.

We report the detection of a glitch event in the Vela pulsar, which occurred on 12 December 2016, based on the timing data obtained from observations between January 2016 and February 2018 at frequency centered at 2256 MHz using the Kunming 40-m radio telescope. The timing solutions for the pre- and post-glitch are presented. By fitting the glitch model to the timing data, we found that the post-glitch recovery exhibits two terms with exponential decay with the time scales of 1 d and 6 d, respectively. The glitch parameters are determined with Δνg/ν=1.431(2)×10−6\\(\\Delta \\nu _{\\mathrm{g}}/\\nu =1.431(2)\\times 10^{-6}\\) and Δν˙g/ν˙=73.354×10−3\\(\\Delta \\dot{\\nu }_{\\mathrm{g}}/\\dot{\\nu }=73.354\\times 10^{-3}\\). The value of the coupling parameter is calculated to be ∼0.08, implying that the core superfluid is probably not involved in this event. For the glitches with two or more terms with exponential decay in the Vela pulsar, we show that the exponential decays usually exhibit longer time scales with higher degree of glitch recovery. The post-glitch behavior in the slow-down rate |ν˙|\\(|\\dot{\\nu }|\\) is dominated by a linear decrease process. From detection of the variations in the slopes of the spin-down rates after the exponential recoveries of the 2013 and 2016 glitches, we conclude that no persistent shift was involved in the 2016 glitches.

This paper describes the work to design a composite bladed marine propeller. The hydrodynamic load and the nonlinear structural responses are predicted by the coupled FEM/CFD method. A pre-twist strategy is used to determine a new geometry of the composite bladed propeller for improving the hydrodynamic performance. Different material schemes and symmetric stacking sequences are considered as the design parameters. An evaluation method of multi-objective function is presented for optimizing the strength, deflection and mass at design conditions. Numerical results are obtained and the optimal design scheme of the composite bladed propeller is obtained.

Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio bursts. Recent observations of a Galactic FRB suggest that at least some FRBs originate from magnetars, but the origin of cosmological FRBs is still not settled. Here we report the detection of 1863 bursts in 82 hr over 54 days from the repeating source FRB~20201124A. These observations show irregular short-time variation of the Faraday rotation measure (RM), which probes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarisation in more than half of the burst sample, including one burst reaching a high fractional circular polarisation of 75%. Oscillations in fractional linear and circular polarisations as well as polarisation angle as a function of wavelength were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetised immediate environment within about an astronomical unit (au; Earth-Sun distance) of the source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy reveal a barred spiral, with the FRB source residing in a low stellar density, interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.

The radio signal transmitted by the Mars Express (MEX) spacecraft was observed regularly between the years 2013-2020 at X-band (8.42 GHz) using the European Very Long Baseline Interferometry (EVN) network and University of Tasmania's telescopes. We present a method to describe the solar wind parameters by quantifying the effects of plasma on our radio signal. In doing so, we identify all the uncompensated effects on the radio signal and see which coronal processes drive them. From a technical standpoint, quantifying the effect of the plasma on the radio signal helps phase referencing for precision spacecraft tracking. The phase fluctuation of the signal was determined for Mars' orbit for solar elongation angles from 0 - 180 deg. The calculated phase residuals allow determination of the phase power spectrum. The total electron content (TEC) of the solar plasma along the line of sight is calculated by removing effects from mechanical and ionospheric noises. The spectral index was determined as \\(-2.43 \\pm 0.11\\) which is in agreement with Kolomogorov's turbulence. The theoretical models are consistent with observations at lower solar elongations however at higher solar elongation (\\(>\\)160 deg) we see the observed values to be higher. This can be caused when the uplink and downlink signals are positively correlated as a result of passing through identical plasma sheets.

In this paper, we investigate the impact of correlated noise on fast radio burst (FRB) searching. We found that 1) the correlated noise significantly increases the false alarm probability; 2) the signal-to-noise ratios (S/N) of the false positives become higher; 3) the correlated noise also affects the pulse width distribution of false positives, and there will be more false positives with wider pulse width. We use 55-hour observation for M82 galaxy carried out at Nanshan 26m radio telescope to demonstrate the application of the correlated noise modelling. The number of candidates and parameter distribution of the false positives can be reproduced with the modelling of correlated noise. We will also discuss a low S/N candidate detected in the observation, for which we demonstrate the method to evaluate the false alarm probability in the presence of correlated noise.Possible origins of the candidate are discussed, where two possible pictures, an M82-harbored giant pulse and a cosmological FRB, are both compatible with the observation.

We present here the analysis of giant micropulses from the Vela pulsar. A total of 4187 giant micropulses with peak flux density \\(>\\)2.5 Jy were detected during almost 4 hours of observations carried out with the Yunnan 40-m radio telescope at 6800 MHz. Nine of the giant micropulses arrived approximately 3 to 4 ms earlier than the peak of average pulse profile, longer than that at lower frequencies. The remaining giant micropulses were clustered into three distributions which correspond to three main emission regions, including four occurring on the trailing edge of averaged profile.