Polarized image of a Schwarzschild black hole with a thin accretion disk as photon couples to Weyl tensor

We have studied polarized image of a Schwarzschild black hole with an equatorial thin accretion disk as photon couples to Weyl tensor. The birefringence of photon originating from the coupling affect the black hole shadow, the thin disk pattern and its luminosity distribution. We also analyze the observed polarized intensity in the sky plane. The observed polarized intensity in the bright region is stronger than that in the darker region. The stronger effect of the coupling on the observed polarized vector appears only in the bright region close to black hole. These features in the polarized image could help us to understand black hole shadow, the thin accretion disk and the coupling between photon and Weyl tensor.

Influence of quintessence dark energy on the shadow of black hole

We investigate the effects of quintessence dark energy on the shadows of black hole, surrounded by various profiles of accretions. For the thin-disk accretion, the images of the black hole comprises the dark region and bright region, including direct emission, lensing rings and photon rings. Although their details depend on the form of the emission, generically, direct emission plays a major role for the observed brightness of the black hole, while the lensing ring makes a small contribution and the photon ring makes a negligible contribution. The existence of a cosmological horizon also plays an important role in the shadows, since the observer in the domain of outer communications is near the cosmological horizon. For spherically symmetric accretion, static and infalling matters are considered. We find that the positions of photon spheres are the same for both static and infalling accretions. However, the observed specific intensity of the image for infalling accretion is darker than for static accretion, due to the Doppler effect of the infalling motion.

Performance Optimization of Original Aluminum Ash Coating

Aluminum ash is a kind of industrial solid waste. Original aluminum ash (OAA) can be prepared into original aluminum ash spray powder (OAASP) through hydrolysis treatment, and the original aluminum ash coating (OAAC) can be prepared on the surface of the substrate by plasma spraying. In order to optimize the performance of the OAAC, the OAASP was screened to select the appropriate particle size to improve the flowability of the powder. Then, the influence of the alumina content on coating performance was studied through comparative experiments. The micro morphology of the coating was analyzed, and the performance parameters of the coating were tested. The results show that the spray powder with a particle size of 120–150 mesh accounts for the largest proportion of OAASP, and its flowability is better than that of unsieved OAASP, which is suitable for coating preparation. The performance of the coating can be improved by adding high-purity alumina. When the Al2O3 addition is 50%, the porosity of the coating is 0.131%, the adhesive strength is 17.12 MPa, the microhardness is 713.36 HV, and the abrasion rate 10.31 mg/min. Compared with the coating without Al2O3, the porosity is decreased by 19.63%, the adhesive strength is increased by 5.35%, the microhardness is increased by 17.61%, and the abrasion rate is decreased by 19.83%. There are regions with different brightness on the surface of the coating with Al2O3. After semiquantitative analysis, the main phase in the bright region is Al2O3, and the main phases in the dark and gray regions are Al2O3, SiO2, and Fe3O4. The performance of the OAAC can be optimized by improving the flowability of the sprayed powder and increasing the alumina content.

Hydrodynamical backflow in X-shaped radio galaxy PKS 2014−55

ABSTRACT We present MeerKAT 1.28 GHz total-intensity, polarization, and spectral-index images covering the giant (projected length l ≈ 1.57 Mpc) X-shaped radio source PKS 2014−55 with an unprecedented combination of brightness sensitivity and angular resolution. They show the clear ‘double boomerang’ morphology of hydrodynamical backflows from the straight main jets deflected by the large and oblique hot-gas halo of the host galaxy PGC 064440. The magnetic field orientation in PKS 2014−55 follows the flow lines from the jets through the secondary wings. The radio source is embedded in faint ($T_\mathrm{b} \approx 0.5 \mathrm{\, K}$) cocoons having the uniform brightness temperature and sharp outer edges characteristic of subsonic expansion into the ambient intragroup medium. The position angle of the much smaller (l ∼ 25 kpc) restarted central source is within 5° of the main jets, ruling out models that invoke jet re-orientation or two independent jets. Compression and turbulence in the backflows probably produce the irregular and low polarization bright region behind the apex of each boomerang as well as several features in the flow with bright heads and dark tails.

Evolution of supersonic downflows in a sunspot

Context. Supersonic downflows have been observed in transition region spectra above numerous sunspots, however, little research has been conducted to date into how persistent these signatures are within sunspots on timescales longer than a few hours. Aims. We aim to analyse the lead sunspot of AR 12526 to infer the properties and evolution of supersonic downflows occurring within it using high-spatial and spectral resolution data. Methods. We analysed 16 large, dense raster scans sampled by the Interface Region Imaging Spectrograph. These rasters tracked the lead sunspot of AR 12526 across the solar disc at discrete times between 27 March 2016 and 2 April 2016, providing spectral profiles from the Si IV, O IV, Mg II, and C II lines. Additionally, we studied one sit-and-stare observation acquired on 1 April 2016 centred on the sunspot to analyse the evolution of supersonic downflows on shorter timescales. Results. Supersonic downflows are variable within this sunspot both in terms of spatial structuring and velocities. Thirteen of the 16 raster scans display some evidence of supersonic downflows in the Si IV 1394 Å line co-spatial to a sustained bright structure detected in the 1400 Å slit-jaw imaging channel; a peak velocity of 112 km s−1 is recorded on 29 March 2016. Evidence for supersonic downflows in the O IV 1401 Å line is found in 14 of these rasters; the spatial structuring in this line often differs from that inferred from the Si IV 1394 Å line. Only one example of a supersonic downflow is detected in the C II 1335 Å line and no downflows are found in the Mg II 2796 Å lines at these locations. In the sit-and-stare observations, no dual flow is initially detected, however, a supersonic downflow develops after approximately 60 min. This downflow accelerates from 73 km s−1 to close to 80 km s−1 in both the Si IV 1394 Å and O IV 1401 Å lines over the course of 20 min before the end of the observation. Conclusions. Supersonic downflows are found in the Si IV 1394 Å line in 13 of the 16 rasters studied in this work. The morphology of these downflows evolved over the course of both hours and days and was often different in the Si IV 1394 Å and O IV 1401 Å lines. These events were found co-spatial to a bright region in the core of the Si IV 1394 Å line, which appeared to form at the footpoints of coronal fan loops. Our results indicate that one raster is not enough to conclusively draw inferences about the properties of supersonic downflows within a sunspot during its lifetime.

Adaptive Tolerance Dehazing Algorithm Based on Dark Channel Prior

The tolerance mechanism based on dark channel prior (DCP) of a single image dehazing algorithm is less effective when there are large areas of the bright region in the hazy image because it cannot obtain the tolerance adaptively according to the characteristics of the image. It will lead to insufficient improvement of the transmission of image, so it is difficult to eliminate the color distortion and block effects in the restored image completely. Moreover, when a dense haze area or a third-party direct light source (sunlight, headlights and reflected glare) is misjudged as sky area, the use of tolerance will cause an inferior dehazing effect such as details lost. Regarding the issue above, this paper proposes an adaptive tolerance estimation algorithm. The tolerance is obtained according to the statistic characteristics of each image to make the estimation of transmission more accurately. The experimental results show that the proposed algorithm not only maintains high operational efficiency but also effectively compensates for the defects of the dark channel prior to some scenes. The proposed algorithm can effectively solve the problem of color distortion recovered by the DCP method in the bright regions of the image.

A Comparative Study of the Phase Separation of a Nematic Liquid Crystal in the Self-assembling Drying Protein Drops

ABSTRACTThe drying process, self-assembly of the proteins and the phase separation of a thermotropic liquid crystal (LC) from an initial aqueous solution represent a rich area of study. A focus of this work is to compare the behavior of two different proteins, bovine serum albumin [BSA] and lysozyme [Lys] in the ternary system through optical microscopy. During the drying process, the intensity profile shows three regimes in the presence of LC whereas no intensity variation is observed in its absence in both protein drops. The striking outcome is the presence of an umbilical defect of [+1] strength in every domain near the edge of BSA drop, whereas, each domain has a central dark region surrounded by a bright region in the dried Lys drop. Finally, the crack spacing in the dried Lys drop is reduced in the presence of LC whereas, no significant difference is found in the dried BSA drop.

Assessment of #TheDress With Traditional Color Vision Tests: Perception Differences Are Associated With Blueness

Based on known color vision theories, there is no complete explanation for the perceptual dichotomy of #TheDress in which most people see either white-and-gold (WG) or blue-and-black (BK). We determined whether some standard color vision tests (i.e., color naming, color matching, anomaloscope settings, unique white settings, and color preferences), as well as chronotypes, could provide information on the color perceptions of #TheDress. Fifty-two young observers were tested. Fifteen of the observers (29%) reported the colors as BK, 21 (40%) as WG, and 16 (31%) reported a different combination of colors. Observers who perceived WG required significantly more blue in their unique white settings than those who perceived BK. The BK, blue-and-gold, and WG observer groups had significantly different color preferences for the light cyan chip. Moreland equation anomaloscope matching showed a significant difference between WG and BK observers. In addition, #TheDress color perception categories, color preference outcomes, and unique white settings had a common association. For both the bright and dark regions of #TheDress, the color matching chromaticities formed a continuum, approximately following the daylight chromaticity locus. Color matching to the bright region of #TheDress showed two nearly distinct clusters (WG vs. BK) along the daylight chromaticity locus and there was a clear cutoff for reporting WG versus BK. All results showing a significant difference involved blue percepts, possibly due to interpretations of the illuminant interactions with the dress material. This suggests that variations in attributing blueness to the #TheDress image may be significant variables determining color perception of #TheDress.