Assessment of community noise for a medium-range airplane with open-rotor engines

Community noise of a hypothetical medium-range airplane equipped with open-rotor engines is assessed by numerical modeling of the aeroacoustic characteristics of an isolated open rotor with the simplest blade geometry. Various open-rotor configurations are considered at constant thrust, and the lowest-noise configuration is selected. A two-engine medium-range airplane at known thrust of bypass turbofan engines at different segments of the takeoff–landing trajectory is considered, after the replacement of those engines by the open-rotor engines. It is established that a medium-range airplane with two open-rotor engines meets the requirements of Chapter 4 of the ICAO standard with a significant margin. It is shown that airframe noise makes a significant contribution to the total noise of an airplane with open-rotor engines at landing.     

Evolution of domain structure and formation of charged domain walls during polarization reversal in lithium niobate single crystals modified by vacuum annealing

The evolution of the domain structure during polarization reversal has been investigated in plates of lithium niobate with spatially inhomogeneous electrical conductivity produced by vacuum annealing. The formation of charged domain walls in the crystal bulk has been studied. Revealed features of the domain growth in the bulk have been attributed to the formation of nanodomains under the pyroelectric field and inhomogeneous spatial distribution of the electric field. Creation of the charged domain walls with controlled parameters is of great interest for domain walls engineering.     

Characterization of PPLN-microstructures by means of Raman spectroscopy

In this paper we show how the Raman microprobe can be used for characterization of the domain structure in periodically poled lithium niobate (PPLN). The Raman scattered intensity of the transverse and longitudinal optical phonons was recorded across the stripe ferroelectric domains at the surface of a z-cut congruent PPLN sample. The change of integrated intensities across the domain structure was attributed to the influence of mechanical stresses and partially screened depolarization fields. PACS 77.80.Dj; 78.30.-j; 77.84.Dy     

Functions harmonic for a Markov process

The compactness property of a family of functions harmonic for a Markov process is studied and, in particular, an inequality of Harnack type is derived. It is shown that under broad conditions the property that a function be locally harmonic implies that it is harmonic.Translated from Matematicheskie Zametki, Vol. 13, No. 4, pp. 587–596, April, 1973.     

Study of the fixation of nitrogen on complex catalysts using N15

Summary Using labeled nitrogen, it was shown that molecular nitrogen is fixed by the system CrCl₃-C₂H₅MgBr.     

Interaction of titanocene generated in the system Cp2TiCl2 + Mg in thf with benzyne and tolane. A novel route to titanaindene and titanacyclopentadiene complexes

Direct synthesis of the titanaindene complex Cp₂Ti[o-C₆H₄C(Ph)C(PH)] through of reaction of tolane with Cp₂Ti and benzyne, generated in the system Cp₂TiCl₂ + Mg + o-fluorobromobenzene in THF is described. Under similar conditions, reaction of Cp₂TiCl₂ with Mg in THF, in the presence of tolane only (ratio Cp₂TiCl₂/Mg/Ph₂C₂ ≈ 1/1/2) yields the titanacyclopentadiene complex Cp₂Tic(Ph)C(Ph)C(PH)C(Ph).     

Coordination chemistry of anticrowns. Complexation of cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 with the cyanoborohydride anion [H3BCN]− and triethylamineborane Et3NBH3

As was shown by IR spectroscopy, the reaction of the three-mercury anticrown (o-C₆F₄Hg)₃ (1) with the [H₃BCN]ion in THF affords the complexes {[(o-C₆F₄Hg)₃][H₃BCN](5) and [(o-C₆F₄Hg)₃]₂[H₃BCN](6). Complex 6 was isolated from solution in the analytically pure state. According to X-ray diffraction data, complex 6 has a double-decker sandwich structure, in which the borohydride group of the [H₃BCN]^? anion is bound to one anticrown molecule by three B-H-Hg bridges, whereas the cyanide group is cooperatively coordinated by three mercury centers of another molecule 1 through the nitrogen atom. The reaction of compound 1 with triethylamineborane Et₃NBH₃ in THF affords the 1: 1 complex ～[(o-C₆F₄Hg)₃][Et₃NBH₃]～ (7). In this adduct, the binding of the aminoborane to the mercury anticrown is also accomplished by B-H-Hg bridges. The stability constants of complexes 5 and 6 in THF were determined.