In recent years, signal processing in encrypted images received much attention from academia due to the privacy preserving property. Reversible data hiding in encrypted images is a technique that ...embedded additional data into an encrypted image without accessing the content of the original image, the embedded data can be extracted and the encrypted image can be recovered to the original one. In this paper, two reversible data hiding methods in encrypted images, namely a joint method and a separable method, are introduced by adopting prediction error. In the joint method, data extraction and image reconstruction are performed at the same time. The reversibility, number of incorrect extracted bits are significantly improved while maintaining good visual quality of recovered image, especially when embedding rate is high. In the separable method, data extraction and image recovery are separated. The separable method also provides improved reversibility and good visual quality of recovered image for high payload embedding.
•Two reversible data hiding methods in encrypted images are proposed.•Improved reversibility is obtained by the two methods.•Visual quality of lossy recovered image by the two methods is high.•The number of incorrect bits is significantly reduced by the joint method.
The recent outbreak of COVID-19 has been rapidly spreading on a global scale. To date, there is no specific vaccine against the causative virus, SARS-CoV-2, nor is there an effective medicine for ...treating COVID-19, thus raising concerns with respect to the effect of risk factors such as clinical course and pathophysiological parameters on disease severity and outcome in patients with COVID-19. By extracting and analyzing all available published clinical data, we identified several major clinical characteristics associated with increased disease severity and mortality among patients with COVID-19. Specifically, preexisting chronic conditions such as hypertension, cardiovascular disease, chronic kidney disease, and diabetes are strongly associated with an increased risk of developing severe COVID-19; surprisingly, however, we found no correlation between chronic liver disease and increased disease severity. In addition, we found that both acute cardiac injury and acute kidney injury are highly correlated with an increased risk of COVID-19-related mortality. Given the high risk of comorbidity and the high mortality rate associated with tissue damage, organ function should be monitored closely in patients diagnosed with COVID-19, and this approach should be included when establishing new guidelines for managing these high-risk patients. Moreover, additional clinical data are needed in order to determine whether a supportive therapy can help mitigate the development of severe, potentially fatal complications, and further studies are needed to identify the pathophysiology and the mechanism underlying this novel coronavirus-associated infectious disease. Taken together, these findings provide new insights regarding clinical strategies for improving the management and outcome of patients with COVID-19.
Pixel expansion and visual quality of the revealed secret image are two major concerns in visual secret sharing (VSS). Random grid (RG) is an alternative approach to solve the pixel expansion problem ...by making the share as big as the original secret image, at the expense of sacrificing the visual quality of the reconstructed secret image. In this paper, two algorithms, including a contrast-enhanced RG-based VSS and a void-and-cluster-based (VAC-based) post-processing, are introduced to improve the reconstructed image quality. Experimental results and theoretical analysis are provided, illustrating that competitive visual quality is obtained by combined use of the two proposed methods.
► We propose two methods to improve the visual quality of RG-based VSS. ► A contrast-enhanced VSS is to increase the contrast of revealed secret image. ► A VAC-based post-processing is adopted to obtain smooth-looking. ► The post-processing can be applied to size invariant probabilistic VSS.
The XOR-based visual cryptography (VC) is a possible methodology to solve the poor visual quality problem without darkening the background in VC. However, investigations on XOR-based VC are not ...sufficient. In this paper, we exploit some extended capabilities for XOR-based VC. Actually, two XOR-based VC algorithms are proposed, namely XOR-based VC for general access structure (GAS) and adaptive region incrementing XOR-based VC. The first algorithm aims to implement complicated sharing strategy using GAS, while maintaining merits such as perfect reconstruction of secret, no pixel expansion, and no code book requirement. In the second algorithm, the concept of adaptive security level is first introduced, where the security levels are recovered in accordance with the qualified sets instead of the quantity of stacked shares. Adaptive region incrementing XOR-based VC further enriches the application scenarios. Theoretical analysis on the proposed algorithms are provided, as well as extensive experimental results and evaluations for demonstrating the effectiveness and advantages of the two methods.
Aiming at the imaging algorithm of high-pulse-repetition random-frequency-hopping synthetic wideband radar on a supersonic/hypersonic aircraft platform, this study established an echo simulation ...model of target and clutter, analyzed the special range-Doppler coupling effect and its influence on imaging, and proposes a method of imaging with pipeline-parallel processing based on generalized 2D matched-filtering and Doppler pre-processing. In the method, Doppler-beam-sharpening was advanced to be performed with the pulse compression process in each frame, and the special range-Doppler coupling effect caused by high dynamic motion of platform and random frequency hopping in bandwidth synthesis was well suppressed; several modes of random frequency hopping were designed and the pipeline-parallel image processing algorithm was optimized for each mode. Theoretical analysis and simulation results show that the proposed imaging method can effectively avoid the divergence of 2D range-Doppler images in the range direction, and can meet the requirements of real-time imaging.
The Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) utilizes the Transposase Tn5 to probe open chromatic, which simultaneously reveals multiple transcription factor binding ...sites (TFBSs) compared to traditional technologies. Deep learning (DL) technology, including convolutional neural networks (CNNs), has successfully found motifs from ATAC-seq data. Due to the limitation of the width of convolutional kernels, the existing models only find motifs with fixed lengths. A Graph neural network (GNN) can work on non-Euclidean data, which has the potential to find ATAC-seq motifs with different lengths. However, the existing GNN models ignored the relationships among ATAC-seq sequences, and their parameter settings should be improved.
In this study, we proposed a novel GNN model named GNNMF to find ATAC-seq motifs via GNN and background coexisting probability. Our experiment has been conducted on 200 human datasets and 80 mouse datasets, demonstrated that GNNMF has improved the area of eight metrics radar scores of 4.92% and 6.81% respectively, and found more motifs than did the existing models.
In this study, we developed a novel model named GNNMF for finding multiple ATAC-seq motifs. GNNMF built a multi-view heterogeneous graph by using ATAC-seq sequences, and utilized background coexisting probability and the iterloss to find different lengths of ATAC-seq motifs and optimize the parameter sets. Compared to existing models, GNNMF achieved the best performance on TFBS prediction and ATAC-seq motif finding, which demonstrates that our improvement is available for ATAC-seq motif finding.
Random grid (RG) is a method to implement visual cryptography (VC) without pixel expansion. However, a reconstructed secret with lower visual quality reveals in RG-based VC due to the fact that ...average light transmission of a share is fixed at 1/2. In this work, we introduce the concept of generalized RG, where the light transmission of a share becomes adjustable, and adopt generalized RG to implement different VC schemes. First, a basic algorithm, a (2,2) generalized RG-based VC, is devised. Based on the (2,2) scheme, two VC schemes including a (2,n) generalized RG-based VC and a (n,n) xor-based meaningful VC are constructed. The two derived algorithms are designed to solve different problems in VC. In the (2,n) scheme, recovered image quality is further improved. In the (n,n) method, meaningful shares are constructed so that the management of shadows becomes more efficient, and the chance of suspicion on secret image encryption is reduced. Moreover, superior visual quality of both the shares and recovered secret image is achieved. Theoretical analysis and experimental results are provided as well, demonstrating the effectiveness and advantages of the proposed algorithms.
A layer-by-layer structure was constructed by alternately arranging conductive layers and insulating layers in a silicone dielectric elastomer (Ecoflex) to largely improve the actuated strain at a ...low electric field. In the electric field environment, the insulating layer blocks the transmission channel of electrons in the adjacent conductive layer, so the interfaces of adjacent conductive layers and insulating layers can accumulate and store a large number of charges, thereby greatly increasing the dielectric constant of the material. Meanwhile, the individual conductive layers are separated by an insulating layer to avoid causing large conductance losses. A high actuated strain (20.33%) at a relatively low electric field (12.5 kV mm−1) and good cyclic stability are obtained on the actuator without any pre-strain. These results demonstrate that our research provides a simple and effective method to significantly improve the actuated strain at a low electric field of DE and promote its practical application.
A new (k,n) threshold secret image sharing scheme with two decoding options is introduced in this paper. The proposed scheme combines color-black-and-white visual cryptography scheme (CBW-VCS) and ...polynomial based secret image sharing (PSIS) together, to offer stacking-to-see decryption and lossless image reconstruction. To construct the color shares, a general (k,n) threshold CBW-VCS is firstly given. A grayscale secret image is converted to a p-radix image and a binary image. The p-radix image is encrypted by the (k,n) PSIS under mod p operation, and n p-radix shadows are obtained. Then, a color share generation algorithm with data embedding is proposed to construct n color shares. Theoretical analysis and sufficient experiments are provided to show the effectiveness and advantages of the proposed scheme.
Rock stratification and anisotropy extensively exist in geothermal reservoir, and have great effects on the results of hot dry rock hydraulic fracturing. Therefore, the understanding of fracturing ...mechanism is critical to successfully building an engineered reservoir with high permeability for enhanced geothermal system. Some previous researchers have attempted to reveal hydraulic fracturing process of stratified rock, but the rock hydraulic fracturing propagation and fracture quality evaluation are still not clear enough. We established a numerical model to study the propagation of non-planar fractures in stratified rock by using extended finite element method. For fracture quality evaluation, we proposed fracture effective length as an index, which is the length of the segment where fracture width greater than 1 mm, considering the volume of sand within injected proppant. It is found that fractures generated from stratified rock is more conducive to heat extraction process. A large in-situ stress difference is more conducive to an increase in the fracture effective length. The methodology and results would guide the perforation location selection for stractified rock hydraulic fracturing process to achieve a reasonable fracture morphology.
•Effective length is the length of the segment where fracture width greater than 1 mm .•Rock stratification increases the fracture effective length.•Relative position of perforation significantly affects fracture morphology.•A large value of in-situ stress difference would reduce the rock initiation pressure.•Perforation position is the most sensitive impact factor on fracture morphology.
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