An image watermarking based on the pdf modeling and quantization effects in the wavelet domain

An image watermarking technique based on the concept of JPEG2000 algorithm is proposed. Biorthogonal wavelet 9/7 transform is used to provide a set of coefficients suitable for watermark embedding. The statistical properties of different subbands are analyzed in order to choose the number of decomposition levels and position of subbands, which will assure the best compromise between the watermark transparency and robustness. The JPEG2000 quantization is applied to avoid insignificant wavelet coefficients, while the remaining ones are used for watermarking. The optimal and blind watermark detection is based on the nonlinear score function and appropriate model of coefficients distribution. The performance of the proposed procedure is tested on examples with various images, showing robustness under different attacks, while maintaining high image quality.     

Denoising of sparse images in impulsive disturbance environment

Multimedia Tools and Applications - The paper presents a method for denoising and reconstruction of sparse images based on a gradient-descent algorithm. It is assumed that the original (non-noisy)...     

Fibonacci Arithmetic Expressions

In this paper, we extend the arithmetic (AR) expressions for functions on finite dyadic groups to functions used in Fibonacci interconnection topologies. We have introduced the Fibonacci-Arithmetic (FibAR) expressions for representation of these functions. We discussed the optimization of FibARs with respect to the number of non-zero coefficients through the Fixed-Polarity FibARs defined by using different polarities for the Fibonacci variables. In this way, we provide a base to extend the application of ARs and related powerful CAD design tools for switching functions to functions in Fibonacci interconnection topologies.     

Relationship between the ambiguity function coordinate transformations and the fractional Fourier transform

It has been shown that the fractional Fourier transform, recently very intensively investigated in mathematics, quantum mechanics, optics and signal processing, can be obtained as a special case of the earlier introduced linear coordinate transformations of the ambiguity function or Wigner distribution. Some applications of the generalized fractional transform on the time-frequency analysis are presented.     

The effect of Cl(I)− ions on kinetics and mechanism of anodic dissolution and cathodic deposition of copper

The influence of Cl(I)^? ions on kinetics and mechanism of anodic dissolution and cathodic deposition of copper in acidic sulfate was investigated. For this investigation the galvanostatic single-pulse method has been used. The results indicate that Cl(I)^? ions change the exchange current density and transfer coefficients as determined from tafel analyses of the anodic and cathodic reactions.     

Pressure drop behaviour in a three-dimensional packed bed cell during copper deposition and hydrogen evolution

Pressure drop in a three-dimensional packed bed electrode cell has been investigated during electrowinning of copper with simultaneous hydrogen evolution. The presence of gas bubbles in the packed bed electrode leads to an increase in the pressure drop in the electrolyte flowing through the cell. This pressure drop increase was in the range of 30 to 70% relative to the bubble-free case. Parameters such as current density, electrolyte velocity and particle shape greatly influence the pressure drop behaviour. Experimental results are correlated using the Ergun equation and show satisfactorily good agreement in the investigated range of modified Reynolds number.     

In-situ immobilization of Sr radioactive isotope using nanocrystalline hydroxyapatite

Hydroxyapatite was used as the inert matrix for in-situ immobilization of strontium (Sr) radioactive isotopes at room temperature. A nano-emulsification method was applied to synthesize Sr-substituted calcium hydroxyapatite (Ca_1?xSr_x)₁₀(PO₄)₆(OH)₂. The concentration of incorporated Sr was in the range of 0 ≤ x ≤ 1. Immobilization of Sr was evaluated using a stable isotope instead of radioactive isotope. The effect of strontium concentration on the crystal structure was studied and the results have showed that in the whole concentration range, Sr forms solid solutions with the host hydroxyapatite crystal structure. Powders comprised of nanometre sized particles were obtained and their properties, such as crystallite and particle size, changes in lattice parameters as function of dopant content and thermal stability, were further examined. It was found that the crystal structure of obtained powders is thermally stable at high temperatures. No secondary phases were formed in as-prepared powders or during calcination. The results in this study showed that nano-emulsion strategy provides a simple pathway for synthesis of a single-phase Sr-substituted hydroxyapatite, which can be used for immobilization of Sr radioactive isotopes.     

Electrochemical synthesis of cupric oxide powder Part I: Influence of pH

Electrochemical synthesis of cupric oxide powder (CuO) in alkaline sodium sulfate is of technological interest. As it is known that hydroxyl ions are needed for the formation of cupric oxide, according to the principal chemical reaction: Cu²⁺ + 2oH^- CuO+H₂ The effect of pH (in the range from 7.50 to 10.80) on cupric oxide powder formation was investigated. Optimum conditions for cupric oxide powder synthesis, with respect to particle size, cell voltage, current efficiency and specific energy consumption were determined to be a pH7.5 and a current density of 4000Am–2. A significant effect of pH on the particle size and aggregation of the powder was confirmed by both galvanostatic measurements and particle size determination. The lowest powder particle sizes were obtained at pH7.5. Aggregation of powder particles at higher pH was also observed.