An integer programming formulation of the key management problem in wireless sensor networks

With the advent of modern communications systems, much attention has been put on developing methods for securely transferring information between constitue     

Optical Diagnostics of Supercritical CO2 and CO2-Ethanol Mixture in the Widom Delta

The supercritical CO₂ (scCO₂) is widely used as solvent and transport media in different technologies. The technological aspects of scCO₂ fluid applications strongly depend on spatial–temporal fluctuations of its thermodynamic parameters. The region of these parameters’ maximal fluctuations on the p-T (pressure-temperature) diagram is called Widom delta. It has significant practical and fundamental interest. We offer an approach that combines optical measurements and molecular dynamics simulation in a wide range of pressures and temperatures. We studied the microstructure of supercritical CO₂ fluid and its binary mixture with ethanol in a wide range of temperatures and pressures using molecular dynamics (MD) simulation. MD is used to retrieve a set of optical characteristics such as Raman spectra, refractive indexes and molecular refraction and was verified by appropriate experimental measurements. We demonstrated that in the Widom delta the monotonic dependence of the optical properties on the CO₂ density is violated. It is caused by the rapid increase of density fluctuations and medium-sized (20–30 molecules) cluster formation. We identified the correlation between cluster parameters and optical properties of the media; in particular, it is established that the clusters in the Widom delta acts as a seed for clustering in molecular jets. MD demonstrates that the cluster formation is stronger in the supercritical CO₂-ethanol mixture, where the extended binary clusters are formed; that is, the nonlinear refractive index significantly increased. The influence of the supercritical state in the cell on the formation of supersonic cluster jets is studied using the Mie scattering technique.     

Influence of Carbon and Oxygen Impurities on Migration Velocity of Grain-boundary Triple Junctions in FCC Metals

Russian Physics Journal - Using molecular dynamics simulation, this paper studies the influence of impurity atoms of carbon and oxygen on the migration velocity of triple junctions of grain...     

Synthesis of superparamagnetic GdFeO3 nanoparticles using a free impinging-jets microreactor

Russian Chemical Bulletin - Gadolinium orthoferrite GdFeO3 nanoparticles were synthesized by co-precipitation of gadolinium and iron(m) hydroxides in a free impinging-jets microreactor followed by...     

Scattering and Absorption of Electromagnetic Waves in the Case of Excitation of Dipole Modes of a Spherical Particle

Radiophysics and Quantum Electronics - We compare the solution to the problem of scattering and absorption of a plane electromagnetic wave by a small spherical particle in the quasistatic dipole...     

Properties of Low Pressure Magnetron Discharge Under the Initiation of Emission Processes on Discharge Electrodes by An Accelerated Ion Beam

Russian Physics Journal - The effect of an ion beam injected along the axis of the anode electrode of a planar magnetron on the ignition of an anomalous low-pressure glow discharge in the magnetron...     

Banach Limits and a Measure on the Set of 0-1-Sequences

Mathematical Notes -     

Rings associated with hyperbolic groups

Abstract We define quasiconvexity cone Qcone(τ) over an infinite hyperbolic (in the sense of Gromov) group τ as the set of conjugacy classes of infinite quasiconvex subgroups H?τ and show that the abelian group of Qcone(τ)-divisors, i.e. finite sums of points from Qcone(τ) with integer coefficients, can be equipped with a natural structure of commutative associative ring with identity. Euler characteristic can be considered as a rational-valued function on Qcone(τ). This approach gives another point of view on the strengthened form of Hanna Neumann's conjecture on the maximal rank of the intersection of two finitely generated subgroups of the free group on two generators.