Adaptation of a Hydroacoustic Communication Channel with OFDM Technology to the Negative Influence of a Drifting Ice Cover

Acoustical Physics - Field investigations of the influence of a drifting ice cover on the probability of bit errors in a hydroacoustic communication channel constructed by the orthogonal...     

New Hybrid Material Based on Multiwalled Carbon Nanotubes Decorated by Rhenium-Tungsten Nanodendrites

Re–W nanoparticles are deposited onto multiwalled carbon nanotubes by the metal organic chemical vapor deposition technique. A mixture of dirhenium decacarbonyl and tungsten hexacarbonyl is used as a precursor. Nanoparticles of hybrid materials are studied by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray phase analysis. It is found that in a wide range of ratios of the precursors (dirhenium decacarbonyl and tungsten hexacarbonyl), the crystalline component is a Re–W phase, and the morphology of the nanoparticles is the same as that of the nanodendrites.     

Passive mode locking and formation of dissipative solitons in electron oscillators with a bleaching absorber in the feedback loop

The mechanisms of passive mode locking and formation of ultrashort pulses in microwave electron oscillators with a bleaching absorber in the feedback loop have been analyzed. It is shown that in the group synchronism regime in which the translational velocity of particles coincides with the group velocity of the electromagnetic wave, the pulse formation can be described by the equations known in the theory of dissipative solitons. At the same time, the regimes in which the translational velocity of electrons differs from the group velocity and the soliton being formed and moving along the electron beam consecutively (cumulatively) receives energy from various electron fractions are optimal for generating pulses with the maximal peak amplitudes.     

An electron diffraction study of 3-methyldiaziridine and 1,2-dimethyldiaziridine

The structures of the title compounds, diaziridines, (the first to be studied in the gas phase) have been determined by electron diffraction. The following principal structural parameters were obtained with the estimated standard deviations parenthesized: 3-methyldiaziridine, N-C = 1.489(9) Å, N-N = 1.444(13) Å, C-C = 1.505(16) Å, C-H = 1.107(5) Å, α =∠ (C-C, NCN) = 61.3° (0.9); 1,2-dimethyldiaziridine, (parameters of the cycle CN₂ were assumed from the previous molecule), N-C (methyl) = 1.445(3) Å, C-H = 1.108(9) Å, ∠ C-N-Me = 112.0° (0.5), the two methyl groups are in the trans position. Vibrational amplitudes were also determined for all important distances.     

Molecular structures of acetylene derivatives of tin: Part III. Gas phase electron diffraction study of tetrakis(trifluoropropynyl)-tin,Sn(CC-CF3)4

A gas phase electron diffraction study of tetrakis(trifluoropropynyl)tin is reported. The model, based on T_d symmetry for the carbon—tin skeleton and C_3v symmetry for the CF₃ groups, refines to the following parameters (bond lengths, r_a, in nm; valence angles in degrees): Sn—C0.2070(7), CC 0.1215(6), C—C 0.1460(7), C—F 0.1343(2), CCF 111.3(0.2). The uncertainties (given in parentheses) represent three times the standard deviation values. The results obtained point to practically free rotation of the CF₃ groups. The presence of electronegative CF₃ causes shortening of the Sn-C bonds in Sn(CC—CF₃)₄ from Me₃SnCCH and Me₃ SnCCSnMe₃. The triple CC bond length is larger than in hexafluoro-2-butyne and nearly the same as in dimethylacetylene.