Semi-blind image restoration based on Chan-Vese denoising model

A semi-blind image restoration algorithm is proposed based on reduced non-convex approximation of Luminita Vese and Tony Chan's(C-V)denoising model.Compared with C-V denoising model,we modify the fidelity term and add a term on point spread function(PSF).The function depends on two variables: the image function to be restored u and the standard deviation of Gaussian kernel to be estimatedσ. Then the problems consist in solving a system with two coupled equations.Compared with the Leah Bar's semi-blind image restoration model which must solve three coupled equations,our method only needs to solve two equations.Furthermore,the estimation of f by our algorithm is superior to Leah Bar's algorithm. The experimental results demonstrate that the proposed method is effective.     

New chaotical image encryption algorithm based on Fisher–Yatess scrambling and DNA coding

Based on the Fisher–Yatess scrambling and DNA coding technology, a chaotical image encryption method is proposed. First, the SHA-3 algorithm is used to calculate the hash value of the initial password, which is used as the initial value of the chaotic system. Second, the chaotic sequence and Fisher–Yatess scrambling are used to scramble the plaintext,and a sorting scrambling algorithm is used for secondary scrambling. Then, the chaotic sequence and DNA coding rules are used to change the plaintext pixel values, which makes the ciphertext more random and resistant to attacks, and thus ensures that the encrypted ciphertext is more secure. Finally, we add plaintext statistics for pixel-level diffusion to ensure plaintext sensitivity. The experimental results and security analysis show that the new algorithm has a good encryption effect and speed, and can also resist common attacks.     

Landauer–Datta–Lundstrom model for terahertz transistor amplifier based on graphene

A transistor has been considered in the form of three electrodes connected by graphene ribbons or by metal quantum wires (nanowires) that operate on the principle of the current control by the changing voltage at the central electrode (gate). The analysis has been carried out according to the Landauer–Datta–Lundstrom model in equilibrium approximation for electrodes while fixing their potentials. We have obtained linear models and nonlinear terms in the determining current, and calculated the nonlinear current–voltage performances of graphene nanoribbons.     

A fusion method for infrared–visible image and infrared-polarization image based on multi-scale center-surround top-hat transform

This paper presents a fusion method for infrared–visible image and infrared-polarization image based on multi-scale center-surround top-hat transform which can effectively extract the feature information and detail information of source images. Firstly, the multi-scale bright (dark) feature regions of source images at different scale levels are respectively extracted by multi-scale center-surround top-hat transform. Secondly, the bright (dark) feature regions at different scale levels are refined for eliminating the redundancies by spatial scale. Thirdly, the refined bright (dark) feature regions from different scales are combined into the fused bright (dark) feature regions through adding. Then, a base image is calculated by performing dilation and erosion on the source images with the largest scale outer structure element. Finally, the fusion image is obtained by importing the fused bright and dark features into the base image with a reasonable strategy. Experimental results indicate that the proposed fusion method can obtain state-of-the-art performance in both aspects of objective assessment and subjective visual quality.     

A new pressure-dominant approximation model for acoustic–structure interaction

A high accuracy approximation modeling approach for the acoustic–structure interaction problem with a shell structure is presented in this paper. The new approximation model aims to accurately reveal the relationship between pressure and velocity in the acoustic field. The main idea of this model is to separate the velocity terms into a combination of velocity and pressure by using a weighting parameter. The modal analysis was performed to find an appropriate weighting parameter for the new model for the spherical case. The stability range of the model is limited during this process. An approximation model was coupled with the equation of motion of a spherical shell to check the performance of the model. Responses of a spherical shell excited by a plane step wave and cosine-type incident pressure from the new model were compared to the exact solution and solutions from former approximation models such as Doubly Asymptotic Approximations (DAAs). The new proposed model can approximate high accuracy responses in both early and late time.     

Single-site approximation for the s–f model of antiferromagnetic semiconductors

For the s–f model of an antiferromagnetic semiconductor, the effect of the antiferromagnetic ordering of the localized spins on the conduction-electron state is investigated over a wide range of exchange strengths by combining the effective-medium approach with the Green's function in the 2×2 sublattice Bloch function representation. The band splitting due to the reduced magnetic Brillouin zone occurs below the Néel temperature. There is a marked effect of the thermal fluctuation of the antiferromagnetically ordered localized spins on the conduction electron at the energies near the top (bottom) of the lower- (higher-) energy subband.     

Speckle reduction algorithm for laser underwater image based on curvelet transform

Based on the analysis on the statistical model of speckle noise in laser underwater image, a novel speckle reduction algorithm using curvelet transform is proposed. Logarithmic transform is performed to transform the original multiplicative speckle noise into additive noise. An improved hard thresholding algorithm is applied in curvelet transform domain. The classical Monte-Carlo method is adopted to estimate the statistics of contourlet coefficients for speckle noise, thus determining the optimal threshold set. To further improve the visual quality of despeckling laser image, the cycle spinning technique is also utilized. Experimental results show that the proposed algorithm can achieve better performance than classical wavelet method and maintain more detail information.     

Novel hybrid image compression–encryption algorithm based on compressive sensing

A new hybrid image compression–encryption algorithm based on compressive sensing is proposed, which can accomplish image encryption and compression simultaneously. The partial Hadamard matrix is adopted as measurement matrix, which is controlled by chaos map. The measurement is scrambled. Compared with the methods adopting the Gaussian random matrix as measurement matrix, and those using the whole measurement matrix as key, the proposed algorithm reduces the burden of transferring key and is more practical. The proposed algorithm with sensitive keys and nice image compression ability can resist various attacks. Simulation results verify the validity and reliability of the proposed algorithm.     

Density functional approximation for van der Waals fluids： based on hard sphere density functional approximation

A universal theoretical approach is proposed which enables all hard sphere density functional approximations (DFAs) applicable to van der Waals fluids. The resultant DFA obtained by combining the universal theoretical approach with any hard sphere DFAs only needs as input a second-order direct correlation function (DCF) of a coexistence bulk fluid, and is applicable in both supercritical and subcritical temperature regions. The associated effective hard sphere density can be specified by a hard wall sum rule. It is indicated that the value of the effective hard sphere density so determined can be universal, i.e. can be applied to any external potentials different from the single hard wall. As an illustrating example, the universal theoretical approach is combined with a hard sphere bridge DFA to predict the density profile of a hard core attractive Yukawa model fluid influenced by diverse external fields; agreement between the present formalism's predictions and the corresponding simulation data is good or at least comparable to several previous DFT approaches. The primary advantage of the present theoretical approach combined with other hard sphere DFAs is discussed.     

Turbulence modulation model for gas–particle flow based on probability density function approach

The paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function(PDF) approach. By means of the PDF method, a general statistical moment turbulence modulation model without considering the trajectory difference between two phases is derived from the Navier–Stokes equations. A new turbulence production term induced by the dispersed-phase is analyzed and considered. Furthermore, the trajectory difference between two media is taken into account. Subsequently, a new k–ε turbulence modulation model in dilute particle-laden flow is successfully set up. Then, the changes to several terms, including the turbulence production, dissipation, and diffusion terms, are well described consequently. The promoted model provides a more probable explanation for the modification of particles on the turbulence. Finally, we applied the model to simulate a gas–particle turbulence flow case in a wall jet, and found that the simulation results agree well with the experimental data.     

An interpretation of the She-Lévêque model based on order statistics

We present an interpretation of the She-Lévêque model in fully developed turbulence based on order statistics. Turbulent behavior at large values of the Reynolds number is often studied through the scaling behavior of moments of the distribution of the velocity differences and of the energy dissipation. The present interpretation leads to a derivation of the scaling exponents ζ_p and τ_p of these moments, without any postulate about a universal relation over the fluctuation structures such as the one used by She and Lévêque. The interpretation is based on the fact that the hierarchy of fluctuation structures imposes statistical constraints, whereupon the order p itself is seen as a random variable. As proposed by She and Lévêque, the hierarchy of the structures is such that the structures of larger order affect locally lower order structures through an entrainment process. This phenomenon leads to the Fisher-Tippett law, one of three asymptotic distributions for the extreme value of a random sample as the size of the sample grows to infinity.     

Lattice Boltzmann model for interface capturing of multiphase flows based on Allen–Cahn equation

A phase-field-based lattice Boltzmann model is proposed for the interface capturing of multi-phase flows based on the conservative Allen–Cahn equation(ACE).By adopting the improved form of a relaxation matrix and an equilibrium distribution function,the time derivative?t(φ)induced by recovering the diffusion term in ACE is eliminated.The conducted Chapman–Enskog analysis demonstrates that the correct conservative ACE is recovered.Four benchmark cases including Zalesak’s disk rotation,vortex droplet,droplet impact on thin film,and Rayleigh–Taylor instability are investigated to validate the proposed model.The numerical results indicate that the proposed model can accurately describe the complex interface deformation.     

Multifractal properties of denaturation process based on Peyrard–Bishop model

DNA has attracted the interest of physicists for a long time. One interesting theoretical question is its melting behavior. The Rényi dimension spectrum of the melting transition of DNA, reveals the multifractal nature of the dynamics of the Peyrard–Bishop model. In this Letter, the effects of different parameters involved in the Peyrard–Bishop model on the multifractal nature of the melting dynamics of a DNA chain are investigated in details. As a result, it can be concluded that not only the best multifractality nature of the model arises from the Morse potential term which is taken in the model but also the multifractal nature of the model is independent of the homogeneity, the length of chain, stacking terms, the thermal bath simulation methods and even the potentials which describe the interaction between the two bases in a pair. Furthermore, our results confirm that, the best potential to describe the interactions between the bases in pairs in the PB and PBD models is the Morse potential.     

Joint precoding and equalization design for reduced-CP OTFS based on the compact input–output model

This work studies the system design for the reduced cycle-prefix (CP) orthogonal time frequency space (OTFS) modulation in which only one CP is inserted in each frame. First, a compact input–output model is established which does not need to assume that the delay and Doppler shifts are on the delay-Doppler sampling grids. Second, based on the proposed compact model, a joint precoding and equalization method is proposed for the reduced-CP OTFS modulation, which can decomposes the whole reduced-CP OTFS communication system into parallel multiple-input multiple-output (MIMO) subsystems. Hence, the computational complexity can be greatly reduced. Simulation results of the bit error rate (BER) performance of the proposed method are reported and compared with the standard method under different system parameters.     

An improved Chan–Vese model by regional fitting for infrared image segmentation

In this paper, a regional fitting method is proposed for infrared image segmentation. In our model, the intensity of each pixel in a region is described by using the sum of the class center and the weighted variance of the region, in order to build energy function for encouraging the similarity pixels to be clustered together. The adoption of such way can thereby eliminate the issue associated with the drift of the class center that is existed in Chan–Vese model. Particularly, followed by incorporating energy function into the level set evolution without re-initialization framework, the variational formulation can force the level set function to be closed to object boundaries. Experiments on some representative and real infrared images have demonstrated that our model has higher performance of segmentation in comparison with Chan–Vese model without re-initialization, and some existing methods, including LBF and LCV model.     

High order resolution of the Maxwell–Fokker–Planck–Landau model intended for ICF applications

A high order, deterministic direct numerical method is proposed for the non-relativistic 2D_x×3D_v$2D_{\mathbf{x}}\times 3D_{\mathbf{v}}$ Vlasov–Maxwell system, coupled with Fokker–Planck–Landau collision operators. The magnetic field is perpendicular to the 2D_x$2D_{\mathbf{x}}$ plane surface of computation, whereas the electric fields occur in this plane. Such a system is devoted to modelling of electron transport and energy deposition in the general frame of Inertial Confinement Fusion applications. It is able to describe the kinetics of the plasma electrons in the nonlocal equilibrium regime, and permits to consider a large anisotropy degree of the distribution function. We develop specific methods and approaches for validation, that might be used in other fields where couplings between equations, multiscale physics, and high dimensionality are involved. Fast algorithms are employed, which makes this direct approach computationally affordable for simulations of hundreds of collisional times.     

New design of triplexer based on metal–insulator–metal plasmonic ring resonators

In this work, we propose a new design of all-optical triplexer based on of metal–insulator–metal（MIM） plasmonic waveguide structures and ring resonators. By adjusting the radii of ring resonators and the gap distance, certain wavelengths can be filtered out and the crosstalk of each channel can also be reduced. The numerical results show that the proposed MIM plasmonic waveguide structure can really function as an optical triplexer with respect to the three wavelengths, that is, 1310, 1490, and 1550 nm, respectively. It can be widely used as the fiber access network element for multiplexer–demultiplexer wavelength selective in fiber-to-the-home communication systems with transmission efficiency higher than 90%. It can also be a potential key component in the applications of the biosensing systems.     

Application of the second—order ground—state correlation and random—phase approximation on photoionization cross section of manganese

Using the many-body perturbation theory,we have calculated the photoionization cross section of 3p and 3d subshells of the neutral manganese,and discussed the second-order ground-state correlation and random-phase approx-imation correlations in detail.This is the first theoretical calculation for manganese as far as we know .our calculated results are more consistent with the experimental results than those given by other methods in the literature.     

Minor hysteresis loops model based on exponential parameters scaling of the modified Jiles–Atherton model

In this present work, the minor hysteresis loops model based on parameters scaling of the modified Jiles–Atherton model is evaluated by using judicious expressions. These expressions give the minor hysteresis loops parameters as a function of the major hysteresis loop ones. They have exponential form and are obtained by parameters identification using the stochastic optimization method “simulated annealing”. The main parameters influencing the data fitting are three parameters, the pinning parameter k, the mean filed parameter α and the parameter which characterizes the shape of anhysteretic magnetization curve a. To validate this model, calculated minor hysteresis loops are compared with measured ones and good agreements are obtained.     

Polymer–ion–clay interaction based model for ion conduction in intercalation-type polymer nanocomposite

A series of polymer nanocomposite films based on intercalation of (PAN)₈LiCF₃SO₃ into the nanometric clay channels of an organomodified clay has been prepared using the standard solution-casting technique. The role of organoclay concentration on polymer–ion interaction, ion–ion interaction, and ion–clay interaction in clay-based nanocomposite films has been analyzed using Fourier transform infrared (FTIR) analysis. Substantial ion dissociation is observed even at a very low clay loading (1–2 wt.%) in the nanocomposites. FTIR results suggest the presence of both uncoordinated CF₃SO₃ ⁻ (free-anions) and ion pairs in the nanocomposite evidenced by changes in CF₃SO₃ ⁻ symmetry from C3ν to Cs and marked asymmetry in the profile of degenerate δ_d(CF₃ ⁻) mode. The experimental results suggest a direct correlation of clay-assisted ion dissociation process with variation in conductivity (σ _dc) and glass transition temperature (T _g) as a function of clay concentration. A model has been proposed to explain the observed correlation on the basis of polymer–ion–clay interaction. The proposed scheme of ion transport mechanism appears to be consistent with the experimental observation.