Compact interrogator for fiber optic Bragg sensors based on an acousto-optic filter formed by photonic crystal rows of air holes

Fiber optic sensors are typically used with expensive tunable lasers or optical spectrum analyzers for wavelength interrogation. We propose to replace the tunable laser by a broadband optical source incorporated with a novel thin linewidth acousto-optic tunable filter. It utilizes optical beam expanders constituted by photonic crystal rows of air holes in LiNbO(3) waveguide. A new design is numerically studied for a short structure (with 32 photonic crystal rows) by a two-dimensional finite-difference time-domain method. Extrapolation of these results to larger structure sizes (about 1 cm) demonstrates the possibility to develop compact interrogators with 0.4 pm wavelength resolution and 40 nm tunable range around 1550 nm.     

Pseudorational rank of a quotient divisible group

We study quotient divisible mixed groups. For these groups we consider the pseudorational rank, a new invariant introduced by A. A. Fomin. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 3, pp. 201–213, 2005.     

On the lattice of all totally composition formations of finite groups

It is shown that the lattice of all totally composition formations of finite groups is algebraic.

     

Determination of the thickness of the surface layer on polymer blocks

A dependence of the thickness of the surface layer on the mechanical and wave characteristics of polymers has been obtained from joint solution of the equations of surface-wave motion and surface-layer equilibrium. From the dependence derived, the thicknesses of the surface layers have been calculated for four polymers. The dependence of surface-layer thickness on mechanical properties of the polymers and loading characteristics has been established.Institute of the Chemistry of High-Molecular-Weight Compounds, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 2, pp. 195–201, March–April, 1972.     

Investigation of correlations in the spectrum of a spark discharge

Journal of Applied Spectroscopy -     

Some morphisms of modules over the ring of pseudorational numbers

We study various morphisms of modules over the ring of pseudorational numbers R. We obtain a criterion for a quasi-isomorphism between finitely generated R-modules, introduce the concept of a pseudohomomorphism, and prove that the Krull-Remak-Schmidt theorem holds in the category of pseudohomomorphisms of finitely generated R-modules.     

Machine learning methods for analyzing user behavior when accessing text data in information security problems

A new method for detecting user access to irrelevant documents based on estimating the document text membership in typical subject areas of the analyzed user is proposed. The typical subject areas are formed using subject area modeling implemented via orthonormal nonnegative matrix factorization. An experimental study with real corporate correspondence formed from an Enron data set demonstrates the high classification accuracy of the proposed method, compared to traditional approaches.     

Novel planar chiral phosphite: Preparation and use in the synthesis of Pd(II) complexes and in Pd-catalyzed allylic alkylation

The planar chiral diaryl phosphorimidite ligand containing additional C-stereocenters and neutral and cationic palladium(II) chelates with this ligand, cis-[Pd(η²-P,N)Cl₂] and [Pd(Allyl)(η²-P,N)]BF₄, were synthesized for the first time. The possibility of using these compounds in asymmetric allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate in an optical yield of up to 73% was demonstrated.