Gd-Bi-M-Ce-O (M = Cu,Zr, Ni,Co, Mn) ceria-based solid solutions for low temperature CO oxidation

Ceria based solid solutions doped by Gd, Bi, and the third dopant were synthesized by the co-precipitation method with ultrasonic treatment, followed by calcination at the temperature of 500°С. Characterization of the synthesized nanosystems by XRD, TEM, TG, Raman spectroscopy, FTIR, XPS was carried out. It is shown that all obtained powders of solid solutions crystallized into a cubic structure of the fluorite type, with an average particle size of 5–15 nm. The samples had a mesoporous structure of the pore diameter of 2–5 nm. The catalytic activity of Gd-Bi-M-Ce-O (M = Cu, Zr, Ni, Co, Mn) solid solutions was carried out. The catalyst Gd_0.05Bi_0.15Mn_0.20Ce_0.60O₂ has the lowest oxidation temperature.     

On conclusive eavesdropping and measures of mutual information in quantum key distribution

We address the question of quantifying eavesdropper’s information gain in an individual attack on systems of quantum key distribution. It is connected with the concept of conclusive eavesdropping introduced by Brandt. Using the BB84 protocol, we examine the problem of estimating a performance of conclusive entangling probe. The question of interest depends on the choice of a quantitative measure of eavesdropper’s information about the error-free sifted bits. The Fuchs–Peres–Brandt probe realizes a very powerful individual attack on the BB84 scheme. In the usual formulation, Eve utilizes the Helstrom scheme in distinguishing between the two output probe states. In conclusive eavesdropping, the unambiguous discrimination is used. Comparing these two versions allows to demonstrate serious distinctions between widely used quantifiers of mutual information. In particular, the so-called Rényi mutual information does not seem to be a completely legitimate measure of an amount of mutual information. It is brightly emphasized with the example of conclusive eavesdropping.     

On Odd-periodic Orbits in Complex Planar Billiards

The famous conjecture of V. Ya. Ivrii (1978) says that in every billiard with infinitely-smooth boundary in a Euclidean space the set of periodic orbits has measure zero. In the present paper, we study the complex version of Ivrii’s conjecture for odd-periodic orbits in planar billiards, with reflections from complex analytic curves. We prove positive answer in the following cases: (1) triangular orbits; (2) odd-periodic orbits in the case, when the mirrors are algebraic curves avoiding two special points at infinity, the so-called isotropic points. We provide immediate applications to k-reflective real analytic pseudo-billiards with odd k, the real piecewise-algebraic Ivrii’s conjecture and its analogue in the invisibility theory: Plakhov’s invisibility conjecture.     

Nanoscopic imaging of oxidized graphene monolayer using tip-enhanced Raman scattering

Nano Research - Tip-enhanced Raman scattering (TERS) can be used for the structural and chemical characterization of materials with a nanoscale resolution, and offers numerous advantages compared...     

Numerical study of the near-field of highly underexpanded turbulent gas jets

For safety issues related to the storage of gases (e.g. hydrogen) under high pressure, it is necessary to determine how the gas is released in the case of failure. In particular, there exist limited quantitative information on the near-field properties of gas jets, which are important for establishing proper decay laws in the far-field. Simulations of the near-field of highly underexpanded (high pressure) gas jets have been performed using Finite-Volume solver of the CAST3M code and validated using several sources available in the literature. The numerical model solves the 3D Compressible Multi-Component Navier–Stokes equations directly without relying on the compressibility-corrected turbulence models. It provides sufficiently fair mean predictions both in the case of one-component air–air and two-component helium-air releases. Possible initial conditions for the far-field simulations are suggested in terms of distance from the source, as well as the turbulence characteristics and gas-dynamic parameters at this location. In addition, these results are used to evaluate several notional nozzle concepts in order to determine the one physically consistent.     

Reducing treatment of coppersmelting slag: Thermodynamic analysis of impurities behavior

A thermodynamic mathematical model, describing behavior of Pb, Zn, and As during reducing slag cleaning in the Vanyukov furnace has been developed. Using a developed model, the influence of different factors, such as temperature, oxygen partial pressure, the ratio of the formed phases on the behavior of impurities, was analyzed. It was found that arsenic can significantly move to the bottom phase, and zinc can be significantly vaporized under conditions in the Vanyukov furnace.     

Effect of silicon content in steel and oxidation temperature on scale growth and morphology

The effect of high silicon content in steel, 1.6 wt.%Si and 3.2 wt.%Si, and high oxidation temperatures (850–1200 °C) on scale growth rate and morphology were investigated. The steels were oxidized in a 15% humid air with short isothermal oxidation times (15 min). The scale growth rate of the non-alloyed steel follows a parabolic law with time; it is an iron diffusion controlled oxidation. The presence of silicon delays scale growth by forming a silica SiO₂ barrier layer at the scale/metal interface, this effect is more important for the steel containing 3.2 wt.%Si and induces a discontinuous scale. Silicon oxides are concentrated at the scale/metal interface; their morphology depends on the oxidation temperature. For temperatures lower than 950 °C, silica is formed. Between 950 °C and 1150 °C, fayalite (Fe₂SiO₄) grains appear in the wüstite matrix close to the scale/metal interface. For temperatures higher than 1177 °C, a fayalite–wüstite eutectic is formed; this molten phase favours iron diffusion leading to high scale growth. After cooling, a continuous fayalite layer with small wüstite grains is obtained at the scale/steel interface.     

A novel clipping technique for filtering FM signals embedded in intensive noise

A novel adaptive clipping technique for filtering a constant amplitude frequency modulated (FM) signal embedded in non-Gaussian noise is proposed. It is based on the analysis and processing of the estimate of probability density function of a FM signal realization. As a result, modifications of two robust estimators of FM signal amplitude are proposed. It is shown that these estimators can be used for Gaussian and non-Gaussian heavy-tail environments. The proposed clipping technique can exploit one or another obtained robust estimate of the signal amplitude for adaptive setting a threshold. Analysis of signal estimate accuracy for different noise environments is carried out. Comparative analysis of the obtained methods and known approaches based on scanning window nonlinear filtering and optimal robust L-DFT form is performed. It is demonstrated that the usage of clipping-based technique leads to the considerable improvement of the FM signal filtering efficiency in comparison to the aforementioned known approaches for different noise environments and a wide range of input SNR values.