Flux Density Variations Research Articles

Plasma lensing near the eclipses of the Black Widow pulsar B1957+20

ABSTRACT Recently, several eclipsing millisecond pulsars have been shown to experience strong and apparent weak lensing from the outflow of their ionized companions. Lensing can be a powerful probe of the ionized plasma, with the strongest lenses potentially resolving emission regions of pulsars. Understanding lensing in the ‘laboratory-like’ conditions of an eclipsing pulsar may be analogously applied to fast radio bursts, many of which reside in dense, magnetized environments. We examined variable dispersion measure (DM), absorption, scattering, and flux density in the original Black Widow pulsar PSR B1957+20 through an eclipse at the Arecibo Observatory at $327\, {\rm MHz}$. We discovered clear evidence of the two regimes of lensing, strong, and apparent weak. We show that the flux density variations in the apparently weak lensing regime can be modelled directly from variations of DM, using geometric optics. The mean effective velocities in the ingress, $(954\pm 99)\, {\rm km\, s^{-1}}$, and egress $(604\pm 47)\, {\rm km\, s^{-1}}$ cannot be explained by orbital motions alone, but are consistent with significant outflow velocity of material from the companion. We also show that geometric optics can predict when and where the lensing regime-change between weak and strong occurs, and argue that the apparent weak lensing is due to averaging many images. Our framework can be applied in any source with variable electron columns, measuring their relative velocities and distances. In other eclipsing pulsars, this provides a unique opportunity to measure companion outflow velocity, predict regions of weak and strong lensing, and in principle independently constrain orbital inclinations.

Relativistic Signatures of Flux Eruption Events near Black Holes

Images of supermassive black holes produced using very long baseline interferometry provide a pathway to directly observing effects of a highly curved spacetime, such as a bright “photon ring” that arises from strongly lensed emission. In addition, the emission near supermassive black holes is highly variable, with bright high-energy flares regularly observed. We demonstrate that intrinsic variability can introduce prominent associated changes in the relative brightness of the photon ring. We analyze both semianalytic toy models and GRMHD simulations with magnetic flux eruption events, showing that they each exhibit a characteristic “loop” in the space of relative photon ring brightness versus total flux density. For black holes viewed at high inclination, the relative photon ring brightness can change by an order of magnitude, even with variations in total flux density that are comparatively mild. We show that gravitational lensing, Doppler boosting, and magnetic field structure all significantly affect this feature, and we discuss the prospects for observing it in observations of M87∗ and Sgr A∗ with the next-generation Event Horizon Telescope.

Variations in Sap Flux Density of Three Urban Tree Species and Their Main Environmental Influencing Factors in Different Timescales in the Beijing Metropolitan Area

Despite the importance of landscape design and water-resources management for urban planning, urban-forest transpiration was seldom estimated in situ. Detailed data on different urban trees’ water resource use and the effect of climatic fluctuations on their transpiration behaviour in different timescales are limited. In this study, we used a thermal dissipation method to measure the sap flux density (Js) of three urban tree species (Pinus tabulaeformis Carrière, Cedrus deodara (Roxb.) G. Don, and Robinia pseudoacacia Linn.) from 1 May 2008 to 30 April 2016 in Beijing Teaching Botanical Garden. The effects of environmental factors on sap flux density (Js) in different timescales were also analyzed. The results showed that there were significant differences in the sap flux density of three trees species in daily, seasonal, and interannual timescales. The hourly, seasonal, and interannual mean sap flux density of Pinus tabulaeformis were higher than that of Cedrus deodara and Robinia pseudoacacia. The seasonal mean Js of Pinus tabulaeformis, Cedrus deodara, and Robinia pseudoacacia in summer were 18.67, 16.19, and 41.62 times that in winter over 2008–2015. The annual mean sap flux density of Pinus tabulaeformis was 1.25–1.72 and 1.26–1.82 times that Cedrus deodara and Robinia pseudoacacia over 2008–2015. The Js responses in three tree species to environmental factors varied differently from daily to interannual timescales. The pattern of day-to-day variation in Js of three urban tree species corresponded closely to air temperature (Ta), soil temperature (Ts), solar radiation (Rs), and vapor pressure deficit (VPD). The Jarvis–Stewart model based on Ta, Rs, and VPD was more suitable for the sap flux density simulation of Pinus tabulaeformis than Cedrus deodara and Robinia pseudoacacia. The main factor affecting the sap flux density of Pinus tabulaeformis and Cedrus deodara was Ta in seasonal timescales. However, the main factor affecting the sap flux density of Robinia pseudoacacia was Ts. The interannual variations in the Js of Pinus tabulaeformis and Robinia pseudoacacia were mainly influenced by wind speed (w) and soil water content (SWC), respectively. The selected environmental factors could not explain the variation in the sap flux density of Cedrus deodara in an interannual timescale. The findings of the present study could provide theoretical support for predicting the water consumption of plant transpiration under the background of climate change in the future.

Interpretation of Time-Varying Radio Emissions of SgrＡ* Observed by 1.3 Millimeter-Wavelength VLBI with Black Hole Binary Concluded by Decameter Radio Wave Pulse Observations

In 2011, by 1.3 mm wavelength VLBI radio wave observations of the SgrA*, Fish, V. L. et al showed that the emissions tightly related to the formation of a black hole shadow have a remarkably large time-varying feature within a region of less than 50 μas. The present paper suggests that the origin of the time variation in the observed emission is due to effects of the orbital motion of the existing super-massive black hole binary orbiting at SgrA* with a period of 2150±2.5 s. This suggestion is based on observations of decameter radio wave pulses from SgrA*. We show a good correlation between the time variation in the coherent flux density of the VLBI results and the time variation model of estimated emission intensities based on the periodic motion of the super-massive black hole binary by applying parameters deduced from the decameter radio wave pulse observation model (DRWP-Model). With further confirmation by Fourier analyses of the potential periodicity of the VLBI data that show the same periods of DRWP Model, we conclude that the time variation detected by the 1.3 mm wavelength radio wave VLBI is evidence of an existing super-massive black hole at Sgr A*.

New formulation of Loss-Surface Model for accurate iron loss modeling at extreme flux density and flux variation: Experimental analysis and test on a high-speed PMSM

The Loss-Surface (LS) model, commonly used for the prediction of iron losses in electrical machines, is reformulated for better accuracy and reliability when it is extrapolated beyond the parametric identification region. First, the dynamic hysteresis behaviors of typical soft magnetic materials are analyzed by both measurements and FE simulations. They are then described by the LS model using different mathematical formulations. The most relevant one, which requires 14 parameters to reproduce and extrapolate any loss surface, will be presented in this paper. The newly reformulated LS model is tested, in the last part, to estimate the iron losses of intrinsic measurements as well as of an electrical machine. In the first case, the results obtained of four different materials are generally within 5% error. And in the latter case of a high speed permanent magnet synchronous motor, by performing a study on the effects of manufacturing methods (punching and assemble) with respect to the iron losses, it is shown that the LS model provides an estimation with around 10% of deviation.

Photosynthetic Active Solar Radiation in Lake Teletskoye During the Open Water Period

Spatial and temporal variability of flux density of photosynthetic active solar radiation (PAR) in the waters of large deep-water oligotrophic Lake Teletskoye (Republic of Altai) is considered based on the analyzed experimental data for the years 2016-2021. Probing of the lake water column was implemented using Satlanic PAR sensor as a part of CTD of the SBE 25plus probe at the beginning and the end of the summer heating period. During various years of studying, PAR magnitude monotonically decreased with lake depth increase and practically became zero at horizons from 3 to 14,8 m according to the data received from two weather stations at the reservoir, i.e. in the pelagic zone of rivers Chulyshman and Kokshi. Flux density of photosynthetic active solar radiation in the upper layer made up to 27-1000 μmol/(m2·s) during the observation period. The photic depth zone (at one percent irradiation) in Lake Teletskoye at the Chulyshman station on sunny days reached 14.8 m, while at the Kokshi one — 11.7 m. According to PAR measurements, the attenuation coefficient (extinction coefficient) along the vertical was estimated as 0.1-2.6 m-1. The maximum weakening coefficient at the Chulyshman station was recorded in June 2016 in the surface 3-m layer of the lake (1.8-2.6 m-1), while below 3 m it had values of 0.1-1.9 m-1. The attenuation coefficient varied within 0.1-1.6 m-1 at the Kokshi station. Relative transparency of the Secchi white disk at the Chulyshman and Kokshi stations ranged within 1.3-5.3 and 2.4-6.5 m, respectively. The paper also presents vertical lake profiles of water temperature in June-July — characteristic of direct summer stratification of the reservoir.

Radio Variability and Broad-Band Spectra of Infrared Galaxies with and without OH Megamaser Emission

We study the radio variability of galaxies with and without sources of hydroxyl (OH) megamaser radiation based on the continuum radio measurements conducted in 2019-2022 with the radio telescope RATAN-600 at frequencies of 2.3, 4.7, 8.2, and 11.2 GHz. Presumably, radio continuum emission significantly affects the megamaser radiation brightness, therefore, such a characteristic as the variability of radio emission is important for determining the OHM galaxies parameters. With additional data from the literature, the parameters of radio variability on a time scale up to 30 years were estimated. The median values of the variability index for 48 OHM galaxies are in the range $V_{S}=0.08$-$0.17$, and for 30 galaxies without OH emission they are $V_{S}=0.08$-$0.28$. For some individual galaxies in both samples, flux density variations reach 30-50%. These sources either are commonly associated with AGNs or reveal active star formation. Generally, the variability of luminous infrared galaxies with and without OH megamaser emission is moderate and of the same order of magnitude on long time scales. From estimating the spectral energy distribution parameters in a broad frequency range (from MHz to THz), we determined the spectral index below 50 GHz and the color temperatures of dust components for megamaser and control sample galaxies. At a level of $\rho<0.05$, there are no statistically significant differences in the distribution of these parameters for the two samples, as well there are no statistically significant correlations between the dust color temperatures and the variability index or luminosity in the OH line.

An orientation bias in observations of submillimetre galaxies

ABSTRACT Recent high-resolution interferometric images of submillimetre galaxies (SMGs) reveal fascinatingly complex morphologies. This raises a number of questions: how does the relative orientation of a galaxy affect its observed submillimetre emission, and does this result in an ‘orientation bias’ in the selection and analysis of such galaxies in flux-limited cosmological surveys? We investigated these questions using the simba cosmological simulation paired with the dust radiative transfer code powderday. We selected eight simulated SMGs (S850 ≳ 2 mJy) at z = 2, and measured the variance of their ‘observed’ emission over 50 random orientations. Each galaxy exhibits significant scatter in its emission close to the peak of the thermal dust emission, with variation in flux density of up to a factor of 2.7. This results in an appreciable dispersion in the inferred dust temperatures and infrared luminosities (16th–84th percentile ranges of 5 K and 0.1 dex, respectively) and therefore a fundamental uncertainty in derived parameters such as dust mass and star formation rate (∼30 per cent for the latter using simple calibrations). Using a Monte Carlo simulation we also assessed the impact of orientation on flux-limited surveys, finding a bias in the selection of SMGs towards those with face-on orientations, as well as those at lower redshifts. We predict that the orientation bias will affect flux-limited single-dish surveys, most significantly at THz frequencies, and this bias should be taken into account when placing the results of targeted follow-up studies in a statistical context.

Constraining the radio properties of the z = 6.44 QSO VIK J2318−3113

The recent detection of the quasi-stellar object (QSO) VIKING J231818.3−311346 (hereafter VIK J2318−3113) at redshift z = 6.44 in the Rapid ASKAP Continuum Survey (RACS) uncovered its radio-loud nature, making it one of the most distant known to date in this class. By using data from several radio surveys of the Galaxy And Mass Assembly 23h field and from a dedicated follow-up, we were able to constrain the radio spectrum of VIK J2318−3113 in the observed range ∼0.1–10 GHz. At high frequencies (0.888–5.5 GHz in the observed frame) the QSO presents a steep spectrum (αr = 1.24, with Sν ∝ ν−αr), while at lower frequencies (0.4–0.888 GHz in the observed frame) it is nearly flat. The overall spectrum can be modelled by either a curved function with a rest-frame turnover around 5 GHz, or with a smoothly varying double power law that is flat below a rest-frame break frequency of about 20 GHz and above which it significantly steepens. Based on the model adopted, we estimated that the radio jets of VIK J2318−3113 must be a few hundred years old in the case of a turnover, or less than a few × 104 years in the case of a break in the spectrum. Having multiple observations at two frequencies (888 MHz and 5.5 GHz), we further investigated the radio variability previously reported for this source. We found that the marginally significant flux density variations are consistent with the expectations from refractive interstellar scintillation, even though relativistic effects related to the orientation of the source may still play a non-negligible role. Further radio and X-ray observations are required to conclusively discern the nature of this variation.

Time variability of cumulative carbon dioxide concentration for adequacy assessment of greenspace: A case study in Surabaya, Indonesia

Introduction: The upward movement of Carbon dioxide (CO2) mass into the air and downwards towards the earth's surface, especially vegetative areas, affected the variability of CO2 concentration in the ambient air. In this pattern, this study aimed to determine the net cumulative value of CO2 concentration (Net_CO2-Con) in an urban area to assess the adequacy of greenspace.&#x0D; Materials and methods: This research method uses CO2 concentration observations within 24 h in 137 observation locations covering an area of 350 km2 in Surabaya city. The sampling location was set at a height of 2 m above the local ground. The CO2 concentration observations were carried out in the dry season and the rainy season for a total of 640 air samples.&#x0D; Results: The results of this study obtained Net_CO2-Con values for ambient CO2 concentrations in a daily pattern. Starting at night there was a flow CO2 flux into the air, which reached its peak in the morning, in about 90% of the city area. This event was evidence of a lack of CO2 absorption due to the lack of extensive vegetative areas. On a bright day the CO2 flux flows towards the land, which indicated the presence of vegetation absorption in addition to soil absorption. The seasonal time variability of CO2 flux density had the same pattern for the daily time variability.&#x0D; Conclusion: Mapping for CO2 flux could be an approach to determine the adequacy of greenspace. Areas of upward movement of CO2 flux density were priority areas for greenspace intensification.&#x0D; &#x0D;

Proximal Remote Sensing-Based Vegetation Indices for Monitoring Mango Tree Stem Sap Flux Density

Plant water use is an important function reflecting vegetation physiological status and affects plant growth, productivity, and crop/fruit quality. Although hyperspectral vegetation indices have recently been proposed to assess plant water use, limited sample sizes for established models greatly astricts their wide applications. In this study, we have managed to gather a large volume of continuous measurements of canopy spectra through proximally set spectroradiometers over the canopy, enabling us to investigate the feasibility of using continuous narrow-band indices to trace canopy-scale water use indicated by the stem sap flux density measured with sap flow sensors. The results proved that the newly developed D (520, 560) index was optimal to capture the variation of sap flux density under clear sky conditions (R2 = 0.53), while the best index identified for non-clear sky conditions was the D (530, 575) (R2 = 0.32). Furthermore, the bands used in these indices agreed with the reported sensitive bands for estimating leaf stomatal conductance which has a critical role in transpiration rate regulation over a short time period. Our results should point a way towards using proximal hyperspectral indices to trace tree water use directly.

New Features of the Pulsar B0950+08 Radiation at the Frequency of 111 MHz

Results of long time observations of the pulsar B0950+08 are given. These observations were carried out at the LPA radio telescope at the frequency of 111 MHz from January of 2016 to May of 2019 (450 days). A strong variability in emission of this pulsar has been detected with changes in signal to noise ratios hundreds of times. Part of the long-time flux density variability can be explained by refractive scintillations in the interstellar medium. The existence of radiation between the interpulse (IP) and main pulse (MP) was confirmed. It was more powerful than at high frequencies. We detected the unusual IP and precursor (Pr) radiation on 2017 August 1. On the basis of 65 strong IPs we found the correlations between energies of IP and Pr and between the phase of IP and the distance Pr–IP. It is shown that the observed peculiarities of this pulsar can be explained in the frame of the aligned rotator model. We estimated distances of radiation levels from the center of the neutron star. The calculated value of the initial period of 0.2 s means that not all pulsars are born with millisecond periods. The large age of the pulsar (6.8 million years) and the small angle between its magnetic moment and the rotation axis (less than 20°) confirm the suggestion related to pulsar evolution with respect to alignment.

The Unanticipated Phenomenology of the Blazar PKS 2131–021: A Unique Supermassive Black Hole Binary Candidate

Abstract Most large galaxies host supermassive black holes in their nuclei and are subject to mergers, which can produce a supermassive black hole binary (SMBHB), and hence periodic signatures due to orbital motion. We report unique periodic radio flux density variations in the blazar PKS 2131−021, which strongly suggest an SMBHB with an orbital separation of ∼0.001–0.01 pc. Our 45.1 yr radio light curve shows two epochs of strong sinusoidal variation with the same period and phase to within ≲2% and ∼10%, respectively, straddling a 20 yr period when this variation was absent. Our simulated light curves accurately reproduce the “red noise” of this object, and Lomb–Scargle, weighted wavelet Z-transform and least-squares sine-wave analyses demonstrate conclusively, at the 4.6σ significance level, that the periodicity in this object is not due to random fluctuations in flux density. The observed period translates to 2.082 ± 0.003 yr in the rest frame at the z = 1.285 redshift of PKS 2131−021. The periodic variation in PKS 2131−021 is remarkably sinusoidal. We present a model in which orbital motion, combined with the strong Doppler boosting of the approaching relativistic jet, produces a sine-wave modulation in the flux density that easily fits the observations. Given the rapidly developing field of gravitational-wave experiments with pulsar timing arrays, closer counterparts to PKS 2131−021 and searches using the techniques we have developed are strongly motivated. These results constitute a compelling demonstration that the phenomenology, not the theory, must provide the lead in this field.

An Improved Fault Detection Method for Overhead Transmission Lines Based on Differential Tunnel Magnetoresistive Sensor Array Approach

Overhead transmission lines play a key role in ensuring power system security and reliability in this current smart society. The overhead transmission line operates in a very complex terrain thereby making it vulnerable to various kinds of faults. Most transmission line faults lead to interruption in power supplies and therefore the need for a fast repair to restore the system to its normal state. A fast, timely, and accurate fault detection technique will ensure speedy restoration of the system thereby reducing outage time. In this article, an enhanced transmission lines’ fault detection approach is presented. This scheme deployed a highly sensitive, low cost, and energy-efficient differential sensor to detect flux density variation measured along transmission lines. The fault detection algorithm is developed for the detection of faults in transmission lines. The development is implemented on a model transmission line and tested for various fault scenarios. Scaled-up laboratory experiments were also conducted to measure magnetic flux density and fault identification to verify the validity of the proposed technique as well as estimate the amount of current produced when a fault occurred. From the simulated and measured current produced during a fault, the proposed technique yielded an estimated error of 1.38%, while the CT and a commercial current probe gave errors of 10.99% and 17.68%, respectively.

Magnetostrictive vibration sensor for a self- powered structural health monitoring system

Previously, we proposed a self-powered vibration-based structural health monitoring system for diagnosing the structural soundness of entire bridges to screen bridges requiring detailed inspection. The core part of the system is the vibration-sensing device that is in the developing phase. This part relies on the Villari effect of magnetostrictive materials. In particular, the vibration-sensing device is a dual-use device that can serve as a vibration sensor and a power generator. This paper describes the design and evaluation results of the device’s performance. Galfenol, a typical magnetostrictive material, was used. Therefore, we first investigate the relationship between the magnetic flux density variation and the compression stress with different bias magnetic fields applied to the Galfenol rod. Moreover, an adequate range of the bias magnetic field was determined to maximize the power-generation performance and sensitivity of vibration. Subsequently, the prototype of the vibration-sensing device was designed and built, and a field test was conducted. The experimental results confirmed that the device works as a vibration sensor with high resolution. The device accurately detected the natural frequency of a bridge, even when subjected to the intermittent load of passing cars. The device generated 30.3 mJ in an hour even though it is a small-sized non-resonant power generator. With such generated energy, diagnosing the structural health at least once every two days can be executed with the developed device.

Simulative study of polymeric core–shell foam particles for the enlargement of the material portfolio in 3‐D high‐frequency welding

AbstractThe steam chest molding process is currently state of the art concerning the generation of three‐dimensional polymeric foam components made from particle foams. An adaption of the high‐frequency welding process shows advantages regarding the required energy and the used water. Due to the low dielectric loss factors of the most common foam materials (PE, PP, and PS), they cannot be heated sufficiently by an electric field. To enable heating of these foams, the particles may be coated with a second material that shows a high dielectric loss. The possible heat development of the modified particles was simulatively investigated. To ensure a realistic simulation, the properties of the used materials are analyzed beforehand. The heating simulation shows clear dependence regarding the particle size and the shell thickness. By a suitable combination, sufficient heating is achievable. For single particles, an irregular temperature distribution is calculated, mainly caused by the difference of permittivity resulting in a local variation of electrical flux density. Bigger particles and thicker shells will result in faster heating ramps and higher overall temperatures. The additional calculation regarding a particle–particle interaction shows a homogenization of the temperature distribution across the particle surface.

CHILES VERDES: Radio Variability at an Unprecedented Depth and Cadence in the COSMOS Field

Abstract Although it is well established that some extragalactic radio sources are time-variable, the properties of this radio variability, and its connection with host galaxy properties, remain to be explored—particularly for faint sources. Here we present an analysis of radio variable sources from the CHILES Variable and Explosive Radio Dynamic Evolution Survey (CHILES VERDES)—a partner project of the 1.4 GHz COSMOS H i Large Extragalactic Survey. CHILES VERDES provides an unprecedented combination of survey depth, duration, and cadence, with 960 hr of 1–2 GHz continuum VLA data obtained over 209 epochs between 2013 and 2019 in a 0.44 deg2 section of the well-studied extragalactic deep field, COSMOS. We identified 18 moderate-variability sources (showing 10%–30% flux density variation) and 40 lower-variability sources (2%–10% flux density variation). They are mainly active galactic nuclei (AGNs) with radio luminosities in the range of 1022–1027 W Hz−1, based on cross-matching with COSMOS multiwavelength catalogs. The moderate-variability sources span redshifts z = 0.22–1.56, have mostly flat radio spectra (α &gt; −0.5), and vary on timescales ranging from days to years. The lower-variability sources have similar properties, but generally have higher radio luminosities than the moderate-variability sources, extending to z = 2.8, and have steeper radio spectra (α &lt; −0.5). No star-forming galaxy showed statistically significant variability in our analysis. The observed variability likely originates from scintillation on short (∼week) timescales, and Doppler-boosted intrinsic AGN variability on long (month–year) timescales.

Impact of the Field Winding Interturn Short-Circuit Position on Rotor Vibration Properties in Synchronous Generators

This paper investigates the effect of the field winding interturn short-circuit (FWISC) position on the rotor vibration properties in turbo generators. Different from the previous studies which focused on the influence of the short-circuit degree, this work pays much attention to the impact of the short-circuit position on the rotor unbalanced magnetic pull (UMP) properties and vibration characteristics. The theoretical UMP model is firstly deduced based on the analysis of the magnetic flux density (MFD) variation. Then, the finite element analysis (FEA) is performed to calculate the UMP data. Finally, the rotor vibrations are tested on a CS-5 prototype generator which has two poles and a rated capacity of 5 kVA. It is shown that the occurrence of FWISC will greatly increase the UMP as well as the rotor vibration. In addition to the short-circuit degree, the short-circuit position will also affect the UMP and vibration. The nearer the short-circuit position is to the big rotor teeth, the larger the UMP and vibration will be. The proposed study in this paper will be beneficial for the monitoring and diagnosis of FWISC faults.

Investigation on magnetometer as potential sensors for infusion pump utilisation status

The utilisation of medical device e.g. an infusion pump is commonly treated as non-trivial process in service and maintenance section albeit in actuality, it is a crucial process for determining its correct maintenance cycle. Therefore, a discussion on the capability of magnetometer sensor as one of potential sensors to be used to keep track the utilisation status of infusion pump. The variation of magnetic flux density and its frequency produced by the stepper motor inside the infusion pump is measured and analysed through magnetometer sensor, embedded inside a Bluetooth Low Energy (BLE) device. Obtained result shows that magnetometer sensor has the potential to track the utilisation status of the tested infusion pumps.

Unusual Emission Variations Near the Eclipse of Black Widow Pulsar PSR J1720−0533

Abstract We report on an unusually bright observation of PSR J1720−0533 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulsar is in a black widow system that was discovered by the Commensal Radio Astronomy FAST Survey (CRAFTS). By coincidence, a bright scintillation maximum was simultaneous with the eclipse in our observation, which allowed for precise measurements of flux density variations, as well as dispersion measure (DM) and polarization. We found that there are quasi-periodic pulse emission variations with a modulation period of ∼22 s during the ingress of the eclipse, which could be caused by plasma lensing. No such periodic modulation was found during the egress of the eclipse. The linear polarization of the pulsar disappears before the eclipse, even before there is a visually obvious change in DM. We also found that the pulse scattering may play an important role in the eclipse of PSR J1720−0533.