Brightness Edge Research Articles

Numerical simulation and experimental study of high-power thermal equilibrium inductively coupled plasma

Inductively coupled plasma generator is one of the core components of the near-space high-speed target plasma electromagnetic scientific experimental research device, which is often used to simulate high enthalpy and high speed plasma sheath environment. In order to study the discharge characteristics of inductively coupled plasma generator under high power, radio frequency and medium pressure, the numerical simulation and experiment are combined to study its internal heat transfer and flow characteristics in this paper. Based on the local thermodynamic equilibrium conditions, the numerical simulation of large-scale radio frequency and medium pressure inductively coupled plasma with a power of 100–400 kW is carried out through the multi-field coupling of flow, electromagnetic and temperature field, and verified by light intensity and spectrum experiment. The results show that the electromagnetic field distribution in the high-power thermal balance inductively coupled plasma generator is similar to that of the small- and medium-sized power plasma generator. The discharge energy dissipation occurs mainly in the area where the induction coil is located. The temperature of the inner wall of the quartz tube is higher at the coil location than in other areas, and the plasma has a ring-shaped high-temperature structure. The outer wall of the quartz tube is set to be the boundary condition of heat flux for simulating the temperature change of the quartz tube under cold blowing. This setting is in coincidence with factual situations. The wall temperature of the quartz tube at the entrance and at the induction coil section are found to be relatively high. When the large-size inductively coupled plasma generator works, an obvious return vortex is generated at the entrance due to the temperature difference and the electromagnetic pumping effect, and the exit velocity increases slightly with the increase of power. At the same time, the discharge experiment under the corresponding conditions shows that there is found a ring structure with bright edges and dark centers in the axial image of the argon discharge. Moreover, the emission spectrum of argon plasma is measured through the spectrum diagnosis system and the spatial distribution of the generator electron temperature is obtained. The light intensity of the discharge image and the electron temperature measured by the spectrum are found to be in comparative coincidence with the COMSOL simulation temperature result, demonstrating the validity of the numerical simulation results under thermodynamic equilibrium conditions. The numerical simulation results in this paper are also applicable to the optimization design and temperature resistance evaluation of the inductively coupled plasma generator.

An Ultrasound Image Enhancement Method Using Neutrosophic Similarity Score.

Ultrasound images, having low contrast and noise, adversely impact in the detection of abnormalities. In view of this, an enhancement method is proposed in this work to reduce noise and improve contrast of ultrasound images. The proposed method is based on scaling with neutrosophic similarity score (NSS), where an image is represented in the neutrosophic domain through three membership subsets T, I, and F denoting the degree of truth, indeterminacy, and falseness, respectively. The NSS measures the belonging degree of pixel to the texture using multi-criteria that is based on intensity, local mean intensity and edge detection. Then, NSS is utilized to extract the enhanced coefficient and this enhanced coefficient is applied to scale the input image. This scaling reflects contrast improvement and denoising effect on ultrasound images. The performance of proposed enhancement method is evaluated on clinical ultrasound images, using both subjective and objective image quality measures. In subjective evaluation, with proposed method, overall best score of 4.3 was obtained and that was 44% higher than the score of original images. These results were also supported by objective measures. The results demonstrated that the proposed method outperformed the other methods in terms of mean brightness preservation, edge preservation, structural similarity, and human perception-based image quality assessment. Thus, the proposed method can be used in computer-aided diagnosis systems and to visually assist radiologists in their interactive-decision-making task.

Colour image enhancement with brightness preservation and edge sharpening using a heat conduction matrix

In this study, an enhancement process obtained by applying the heat conduction equation of solid and stagnant fluids on colour images is proposed. After the colour channel stretching, the RGB colour image was converted to the HSI model. The heat conduction equation was applied for each pixel on the I channel of the HSI colour model. The elements of the feature matrix called heat conduction matrix (HCM) can have negative, positive or zero values. A pixel with a small negative HCM value indicates that I needs level enhancement for a good image, whereas a small positive HCM value means that the I level value will be reduced and aligned with its neighbours. High positive or negative values are defined as the edges of the objects and the I level values of such pixels are not changed to protect the edges. In addition, whether HCM is negative or positive, the balanced increment and decrement path at a level I ensures that the mean brightness value performs natural protection. Finally, an enhanced image is obtained by transitioning from the HSI to the RGB colour model. Experimental results show that this method can enhance colour image details better than other methods.

X-ray study of the merging galaxy cluster Abell 3411-3412 with XMM-Newton and Suzaku

Context. Previous Chandra observations of the Abell 3411-3412 merging galaxy cluster system revealed an outbound bullet-like sub-cluster in the northern part and many surface brightness edges at the southern periphery, where multiple diffuse sources are also reported from radio observations. Notably, a southeastern radio relic associated with fossil plasma from a radio galaxy and with a detected X-ray edge provides direct evidence of shock re-acceleration. The properties of the reported surface brightness features have yet to be constrained from a thermodynamic viewpoint. Aims. We use the XMM-Newton and Suzaku observations of Abell 3411-3412 to reveal the thermodynamical nature of the previously reported re-acceleration site and other X-ray surface brightness edges. We also aim to investigate the temperature profile in the low-density outskirts with Suzaku data. Methods. We performed both imaging and spectral analysis to measure the density jump and the temperature jump across multiple known X-ray surface brightness discontinuities. We present a new method to calibrate the vignetting function and spectral model of the XMM-Newton soft proton background. Archival Chandra, Suzaku, and ROSAT data are used to estimate the cosmic X-ray background and Galactic foreground levels with improved accuracy compared to standard blank sky spectra. Results. At the southeastern edge, temperature jumps revealed by both XMM-Newton and Suzaku point to a ℳ ∼ 1.2 shock, which agrees with the previous result from surface brightness fits with Chandra. The low Mach number supports the re-acceleration scenario at this shock front. The southern edge shows a more complex scenario, where a shock and the presence of stripped cold material may coincide. There is no evidence for a bow shock in front of the northwestern “bullet” sub-cluster. The Suzaku temperature profiles in the southern low-density regions are marginally higher than the typical relaxed cluster temperature profile. The measured value kT500 = 4.84 ± 0.04 ± 0.19 keV with XMM-Newton and kT500 = 5.17 ± 0.07 ± 0.13 keV with Suzaku are significantly lower than previously inferred from Chandra.

NGC 4869 in the Coma Cluster: Twist, Wrap, Overlap, and Bend

Abstract The upgraded Giant Metrewave Radio Telescope (GMRT) has been used to image the head–tail radio galaxy NGC 4869 in the Coma cluster with an angular resolution of 6.″26 at 250–500 MHz and 2.″18 at the 1050–1450 MHz bands. The archival legacy GMRT data have also been used to image the source with angular resolutions from 4.″9 to 21.″8 at 610 MHz, 325 MHz, 240 MHz, and 150 MHz. We find that the ∼200 kpc scale radio morphology consists of five distinct regions with the clear presence of a pinch at ≈1.′4 (=38.8 kpc) and a ridge at ≈3.′4 (=94.2 kpc) from the head. The sharp bend by ∼70° at ∼3.′5 (=97 kpc) from the head is possibly due to projection effects. The radio spectra show progressive spectral steepening as a function of distance from the head and there is possibly re-acceleration of the synchrotron electrons and perhaps also magnetic field regeneration in the 6″–208″ (=2.8–96.1 kpc) region of the jet. We report a steep spectrum sheath layer enveloping a flat spectrum spine, hinting at a transverse velocity structure with a fast-moving spine surrounded by a slow-moving sheath layer. We also derive the lifetimes of the radiating electrons and equipartition parameters. A plausible explanation for the characteristic feature, a ridge of emission perpendicular to the direction of tail is the flaring of a straight, collimated radio jet as it crosses a surface brightness edge due to Kelvin–Helmholtz instabilities.

Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

ABSTRACT We present the results of deep Chandra and XMM–Newton observations of a complex merging galaxy cluster Abell 2256 (A2256) that hosts a spectacular radio relic (RR). The temperature and metallicity maps show clear evidence of a merger between the western subcluster (SC) and the primary cluster (PC). We detect five X-ray surface brightness edges. Three of them near the cluster centre are cold fronts (CFs): CF1 is associated with the infalling SC; CF2 is located in the east of the PC; and CF3 is located to the west of the PC core. The other two edges at cluster outskirts are shock fronts (SFs): SF1 near the RR in the NW has Mach numbers derived from the temperature and the density jumps, respectively, of MT = 1.62 ± 0.12 and Mρ = 1.23 ± 0.06; SF2 in the SE has MT = 1.54 ± 0.05 and Mρ = 1.16 ± 0.13. In the region of the RR, there is no evidence for the correlation between X-ray and radio substructures, from which we estimate an upper limit for the inverse-Compton emission, and therefore set a lower limit on the magnetic field (∼ 450 kpc from PC centre) of B > 1.0 μG for a single power-law electron spectrum or B > 0.4 μG for a broken power-law electron spectrum. We propose a merger scenario including a PC, an SC, and a group. Our merger scenario accounts for the X-ray edges, diffuse radio features, and galaxy kinematics, as well as projection effects.

Application of electron channeling contrast imaging to 3D semiconductor structures through proper detector configurations

Nowadays electron channeling contrast imaging (ECCI) is widely used to characterize crystalline defects on blanket semiconductors. Its further application in the semiconductor industry is however challenged by the emerging rise of nanoscale 3D heterostructures. In this study, an angular multi-segment detector is utilized in backscatter geometry to investigate the application of ECCI to the defect analysis of 3D semiconductor structures such as III/V nano-ridges. We show that a low beam energy of 5 keV is more favorable and that the dimension of 3D structures characterized by ECCI can be scaled down to ~ 28 nm. Furthermore, the impact of device edges on the collected ECCI image is investigated and correlated with tool parameters and cross-section profiles of the 3D structures. It is found that backscattered electrons (BSE) emitted from the device edge sidewalls and generating the bright edges (edge effects), share a similar angular distribution to those emitted from the surface. We show that the collection of low angle BSEs can suppressed the edge effects, however, at the cost of losing the defect contrast. A positive stage bias suppresses edge effects by removing the inelastically backscattered electrons from the sidewalls, but low loss BSEs from the sidewalls still contribute to the ECCI micrographs. On the other hand, if segments of an angular backscatter (ABS) detector are properly aligned with the nano-ridges, BSEs emitted from the sidewall and the surface can be separated, thus leading to the completely absence of one bright edge on the surface without compromise of the defect contrast. The merging of two such ECCI images reveals the nano-ridge surface without edge effects.

Spinal cord MRI contrast enhancement using adaptive gamma correction for patient with multiple sclerosis

Magnetic resonance imaging (MRI) is a clinically important tool for diagnosing several neurological diseases such as the multiple sclerosis (MS). Brain MRI has always facilitated the examination of the MS pathology. Moreover, spinal cord MRI is greatly suggested for the management of such disease, even though the use of conventional spinal cord MRI can be a challenging task. In fact, it is a long and fine organ that has some mobility and that suffers from breathing artifacts, low contrast, heartbeat and cerebro-spinal fluid flows. In this study, to identify spinal cord damage in MS patient, an adaptive MRI contrast enhancement (CE), called the LL-GAGC method, is proposed. This novel technique is based on a combination of the adaptive gamma correction and the discrete wavelet transform with singular value decomposition algorithms. The main reason of this association is to enhance adaptively the contrast of dark MR images while preserving edge information from any distortion. A large database formed by 112 T2-w spinal cord MR images was examined for assessment of the proposed LL-GAGC CE method. Qualitative and quantitative evaluations demonstrated that our proposed algorithm performs well in enhancing the contrast of dark MR images with the benefit of preserving brightness information and edges details.

Chandra observation of a cold front in Abell 2554

Abstract We present the evidence for the existence of sub-structure in the cold front cluster A2554 based on a 20.14 ks Chandra observation. Using centroid shift and X-ray brightness concentration parameters, we confirm that A2554 is a dynamically disturbed system. We detect two dominant structures: a main cluster at z = 0.1108 and a foreground northern sub-structure at z = 0.1082. The analysis reveals an X-ray surface brightness edge at r ≃ 60 h−1 kpc from the cluster core. The thermodynamical profiles across the edge are ruling out the shock scenario. The temperature jump (from ∼6 keV to ∼10 keV), and pressure equilibrium (P0/P1 = 1.01 ± 0.23) across the edge, are consistent with the definition of a cold front with a Mach number $\mathcal {M}_1=0.94^{+0.13}_{-0.17}$. We also observed a weak bow-shock at ∼100 kpc in front of the cold cloud, corresponding an upper limit to the Mach number $\mathcal {M}_1$ ∼1.1. If the northern sub-structure was not related to the cold front, we conclude that the transonic motion of the cloud is caused by a merger, which was weak or occurred long ago.

AGN Feedback in Galaxy Groups: A Detailed Study of X-Ray Features and Diffuse Radio Emission in IC 1262

Abstract This paper reports a systematic search of X-ray cavities, density jumps, and shocks in the intergalactic environment of the galaxy group IC 1262 using Chandra, GMRT, and Very Large Array archival observations. The X-ray imaging analysis reveals a pair of X-ray cavities to the north and south of the X-ray peak, at projected distances of 6.48 kpc and 6.30 kpc respectively. Total mechanical power contained in both of these cavities is found to be ∼12.37 × 1042 erg s−1, and compares well with the X-ray luminosity, within the cooling radius, measured to be ∼3.29 × 1042 erg s−1, suggesting that the mechanical power injected by the central AGN efficiently balances the radiative loss. We detect a previously unknown X-ray cavity at the position of the southern radio lobe in the intra-group medium and find a loop of excess X-ray emission extending ∼100 kpc southwest from the central galaxy. The X-ray cavity at the position of the southern radio lobe probably represents a first generation X-ray cavity. Two surface brightness edges are evident to the west and northeast of the center of this group. The radio galaxy at the core of the IC 1262 group is a rare low-redshift ultra-steep radio galaxy, its spectral index being α ∼ −1.73 (including the central AGN) and α ∼ −2.08 (excluding the central AGN). We detect a radio phoenix embedded within the southern radio lobe, for the first time in a poor group, with a spectral index (α ≤ −1.92). The spectral index distribution across the phoenix steepens with increasing distance from its intensity peak.

Coverless Image Steganography: A Survey

With the digitalization of information, a lot of multimedia data are under attack, information security has become a key issue of public concern. Image steganography, aiming at using cover images to convey secret information has become one of the most challenge and important subjects in the field of information security recently. Different from the traditional image steganography, coverless image steganography does not need to employ the designated cover image for embedding the secret data but directly transfers secret information through its own properties such as pixel brightness value, color, texture, edge, contour and high-level semantics. Therefore, it radically resist the detection of steganalysis tools and significantly improves the security of the image. Its basic idea is to analyze the attributes of the image and map them to the secret information according to certain rules based on the characteristics of the attributes. This paper includes more than 50 key contributions to provide a comprehensive survey in this field, covers the main aspects of coverless image steganography research: the fundamental frameworks, pre-processing, feature extraction, generation of hash sequence and mapping relationships. The existing methods are evaluated and the prospect of future work is also summarized.

Screen Content Image Quality Assessment With Edge Features in Gradient Domain

Objective visual quality assessment specific for screen content images (SCIs) has been increasingly investigated over the years. In this paper, an effective full-reference quality evaluation model for SCIs is proposed, in which edge features in gradient domain (EFGD) are extracted for better visual perceptual representation. Unlike traditional edge feature extraction directly in the image pixel domain, all edge features in the proposed EFGD model are extracted based on the gradient map of input SCIs, including edge sharpness, edge brightness/contrast, and edge chrominance. Specifically, the gradient profile model that can well represent the spatial layout of edges is adopted to measure the edge sharpness degree. A novel computation way is reported to measure the edge brightness and contrast change between the reference and distorted SCIs, while color moments are used to account for the color chrominance variation. In addition, an adaptive weighting strategy is designed to adjust the effects of these three kinds of edge features, according to the statistical distributions of the input SCIs. Moreover, the maximum value of edge sharpness features is extracted from the test SCIs as the pooling weight to get the final image quality assessment (IQA) score. The experimental results on two commonly used SCIs databases have verified the superiorities of the EFGD model and show that the EFGD model is in more conformity with the subjective assessment results than most of the existing IQA models.

A combined X-ray, optical, and radio view of the merging galaxy cluster MACS J0417.5–1154

We present a comprehensive multi-wavelength analysis of the merging galaxy cluster MACS~J0417.5-1154 at a redshift of $z=0.44$, using available images red obtained with \chandra\ in X-ray, {\it Subaru}, {\it Hubble Space Telescope} (HST) in optical, {\it Giant Metrewave Radio Telescope} (GMRT) in radio and {\it Bolocam} at 2.1~mm wavelength. This is an example of a complex merging galaxy cluster also hosting a steep-spectrum Mpc scale radio halo. The mass distribution obtained by weak lensing reconstruction shows that MACS~J0417.5-1154 belongs to the dissociative class of mergers, where one of its substructures has had its gas content detached after the pericentric passage. We find the main cluster mass $M_{200}~=~11.5^{+3.0}_{-3.5} \times 10^{14}\ M_\odot$ and the smaller second (sub)cluster mass to be $M_{200}~=~1.96^{+1.60}_{-0.95} \times 10^{14}\ M_\odot$, leading to a large total mass of $M_{200}~=~13.8^{+2.6}_{-2.8} \times 10^{14}\ M_\odot$. The overall structure, surface brightness profile, temperature and metal abundance of the intra-cluster medium (ICM) all point towards the presence of a cold front and merger induced gas-sloshing motion near the core. We detect a surface brightness edge to the south$-$east direction at a projected distance of $\sim$45 arcsec ($\sim$255\,kpc) from the centre of this cluster. The X-ray spectral analysis across the inner and outer edge allows us to confirm the detected edge as a cold front. The GMRT 235\,MHz observation shows a comet$-$like extended sychrotron radio halo emission trailing behind the cold front. The peak of the Sunyaev-Zel'dovich decrement is found displaced from the centre of X-ray emission, which is interpreted as consequence of the merger dynamics.

Wavelet Decomposition–Based Speckle Reduction Method for Ultrasound Images by Using Speckle-Reducing Anisotropic Diffusion and Hybrid Median

Ultrasound imaging is considered as a common facility of imaging techniques used in medical field because of its benefits, but the quality of ultrasound image is affected and degraded by the type of noise generated by the backscattered signals that interfere with each other and introduce a random interference pattern. This pattern is called speckle. In this article, we develop a new denoising method by introducing a speckle-reducing anisotropic diffusion filter into 4 sub-band images gained by using 2-dimensional wavelet decomposition. Moreover, according to frequency content on each sup band, we use hybrid median filter to get a full advantage of using nonlinear filtering in speckle noise. Finely to improve the quality of image and the overall performance, total variation is used in view of it is capability of brightness equality and edges preserving. The experimental result shows that the proposed method is highly effective in noise separation as well as edges preserving based on compression between linear scaling of the gray-level values despeckle filter, speckle-reducing anisotropic diffusion, median, hybrid median filter, and wavelet filters using image quality evaluation metrics.

Edge Modeling by Two Blur Parameters in Varying Contrasts.

This paper presents a method of modeling edge profiles with two blur parameters, and estimating and predicting those edge parameters with varying brightness combinations and camera-to-object distances (COD). First, the validity of the edge model is proven mathematically. Then, it is proven experimentally with edges from a set of images captured for specifically designed target sheets and with edges from natural images. Estimation of the two blur parameters for each observed edge profile is performed with a brute-force method to find parameters that produce global minimum errors. Then, using the estimated blur parameters, actual blur parameters of edges with arbitrary brightness combinations are predicted using a surface interpolation method (i.e., kriging). The predicted surfaces show that the two blur parameters of the proposed edge model depend on both dark-side edge brightness and light-side edge brightness following a certain global trend. This is similar across varying CODs. The proposed edge model is compared with a one-blur parameter edge model using experiments of the root mean squared error for fitting the edge models to each observed edge profile. The comparison results suggest that the proposed edge model has superiority over the one-blur parameter edge model in most cases where edges have varying brightness combinations.

Estimation of severity level of non-proliferative diabetic retinopathy for clinical aid

Diabetic retinopathy, a symptomless complication of diabetes, is one of the significant causes of vision impairment in the world. The early detection and diagnosis can reduce the occurrence of severe vision loss due to diabetic retinopathy. The diagnosis of diabetic retinopathy depends on the reliable detection and classification of bright and dark lesions present in retinal fundus images. Therefore, in this work, reliable segmentation of lesions has been performed using iterative clustering irrespective of associated heterogeneity, bright and faint edges. Afterwards, a computer-aided severity level detection method is proposed to aid ophthalmologists for appropriate treatment and effective planning in the diagnosis of non-proliferative diabetic retinopathy. This work has been performed on a composite database of 5048 retinal fundus images having varying attributes such as position, dimensions, shapes and color to make a reasonable comparison with state-of-the-art methods and to establish generalization capability of the proposed method. Experimental results on per-lesion basis show that the proposed method outperforms state-of-the-methods with an average sensitivity/specificity/accuracy of 96.41/96.57/94.96 and 95.19/96.24/96.50 for bright and dark lesions respectively on composite database. Individual per-image based class accuracies delivered by the proposed method: No DR-95.9%, MA-98.3%, HEM-98.4%, EXU-97.4% and CWS-97.9% demonstrate the clinical competence of the method. Major contribution of the proposed method is that it efficiently grades the severity level of diabetic retinopathy in spite of huge variations in retinal images of different databases. Additionally, the substantial combined performance of these experiments on clinical and open source benchmark databases support a strong candidature of the proposed method in the diagnosis of non-proliferative diabetic retinopathy.

A generalized method for the segmentation of exudates from pathological retinal fundus images

Diabetic retinopathy, an asymptomatic complication of diabetes, is one of the leading causes of blindness in the world. The exudates, abnormal leaked fatty deposits on retina, are one of the most prevalent and earliest clinical signs of diabetic retinopathy. In this paper, a generalized exudates segmentation method to assist ophthalmologists for timely treatment and effective planning in the diagnosis of diabetic retinopathy is developed. The main contribution of the proposed method is the reliable segmentation of exudates using dynamic decision thresholding irrespective of associated heterogeneity, bright and faint edges. The method is robust in the sense that it selects the threshold value dynamically irrespective of the large variations in retinal fundus images from varying databases. Since no performance comparison of state of the art methods is available on common database, therefore, to make a fair comparison of the proposed method, this work has been performed on a diversified database having 1307 retinal fundus images of varying characteristics namely: location, shapes, color and sizes. The database comprises of 649 clinically acquired retinal fundus images from eye hospital and 658 retinal images from publicly available databases such as STARE, MESSIDOR, DIARETDB1 and e-Optha EX. The segmentation results are validated by performing two sets of experiments namely: lesion based evaluation criteria and image based evaluation criteria. Experimental results at lesion level show that the proposed method outperforms other existing methods with a mean sensitivity/specificity/accuracy of 88.85/96.15/93.46 on a composite database of retinal fundus images. The segmentation results for image-based evaluation with a mean sensitivity/specificity/accuracy of 94.62/98.64/96.74 respectively prove the clinical effectiveness of the method. Furthermore, the significant collective performance of these experiments on clinically as well as publicly available standard databases proves the generalization ability and the strong candidature of the proposed method in the real-time diagnosis of diabetic retinopathy.

Suzaku and Chandra observations of the galaxy cluster RXC J1053.7+5453 with a radio relic

Abstract We present the results of Suzaku and Chandra observations of the galaxy cluster RXC J1053.7+5453 (z = 0.0704), which contains a radio relic. The radio relic is located at a distance of ∼540 kpc from the X-ray peak toward the west. We measured the temperature of this cluster for the first time. The resultant temperature in the center is ∼1.3 keV, which is lower than the value expected from the X-ray luminosity–temperature and the velocity dispersion–temperature relations. Though we did not find a significant temperature jump at the outer edge of the relic, our results suggest that the temperature decreases outward across the relic. Assuming the existence of the shock at the relic, its Mach number becomes M ≃ 1.4. A possible spatial variation of Mach number along the relic is suggested. Additionally, a sharp surface brightness edge is found at a distance of ∼160 kpc from the X-ray peak toward the west in the Chandra image. We performed X-ray spectral and surface brightness analyses around the edge with the Suzaku and Chandra data, respectively. The obtained surface brightness and temperature profiles suggest that this edge is not a shock but likely a cold front. Alternatively, it cannot be ruled out that thermal pressure is really discontinuous across the edge. In this case, if the pressure across the surface brightness edge is in equilibrium, other forms of pressure sources, such as cosmic-rays, are necessary. We searched for the non-thermal inverse Compton component in the relic region. Assuming a photon index Γ = 2.0, the resultant upper limit of the flux is 1.9 × 10−14 erg s−1 cm−2 for a 4.50 × 10−3 deg2 area in the 0.3–10 keV band, which implies that the lower limit of magnetic field strength becomes 0.7 μG.

Haze Removal Using Radial Basis Function Networks for Visibility Restoration Applications.

Restoration of visibility in hazy images is the first relevant step of information analysis in many outdoor computer vision applications. To this aim, the restored image must feature clear visibility with sufficient brightness and visible edges, while avoiding the production of noticeable artifacts. In this paper, we propose a haze removal approach based on the radial basis function (RBF) through artificial neural networks dedicated to effectively removing haze formation while retaining not only the visible edges but also the brightness of restored images. Unlike traditional haze-removal methods that consist of single atmospheric veils, the multiatmospheric veil is generated and then dynamically learned by the neurons of the proposed RBF networks according to the scene complexity. Through this process, more visible edges are retained in the restored images. Subsequently, the activation function during the testing process is employed to represent the brightness of the restored image. We compare the proposed method with the other state-of-the-art haze-removal methods and report experimental results in terms of qualitative and quantitative evaluations for benchmark color images captured in typical hazy weather conditions. The experimental results demonstrate that the proposed method is able to produce brighter and more vivid haze-free images with more visible edges than can the other state-of-the-art methods.

MACS J0553.4−3342: a young merging galaxy cluster caught through the eyes of Chandra and HST

We present a detailed analysis of a young merging galaxy cluster \mac~(z=0.43), from {\it Chandra} X-ray and {\it Hubble Space Telescope} archival data. X-ray observations confirm that the X-ray emitting intra-cluster medium (ICM) in this system is among the hottest (average $T=12.1 \pm 0.6$ keV) and most luminous known. Comparison of X-ray and optical images confirm that this system hosts two merging subclusters SC1 and SC2, separated by a projected distance of about 650\,kpc. The subcluster SC2 is newly identified in this work, while another subcluster (SC0), previously thought to be part of this merging system, is shown to be possibly a foreground object. Apart from two subclusters, we find a tail-like structure in the X-ray image, extending to a projected distance of $\sim$1\,Mpc, along the north-east direction of the eastern subcluster (SC1). From a surface brightness analysis, we detect two sharp surface brightness edges at $\sim$40$\arcsec$ ($\sim$320\,kpc) and $\sim$80$\arcsec$ ($\sim$640\,kpc) to the east of SC1. The inner edge appears to be associated with a merger-driven cold front, while the outer one is likely to be due to a shock front, the presence of which, ahead of the cold front, makes this dynamically disturbed cluster interesting. Nearly all the early-type galaxies belonging to the two subclusters, including their BCGs, are part of a well-defined red sequence.