Boxnep - модульный подводный робот перспективных технологий

The article discusses the relevance of the underwater vehicles are able to solve a wide range of problems. The decision puts in a basis of the research is designing a modular underwater robot. It allows to make a mounting of various equipment and testing it in the water medium. The paper deals with the concept of the robot and its characteristics

Broad-band dielectric spectroscopy of Ba

Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 102–1014 Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at $T_{\rm c}=830$ K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear on cooling in the ferroelectric phase. Below Ti the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling for the ${\vec E}\bot {\vec c}$ field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman active B2-symmetry soft mode

Dielectric relaxation in tetragonal tungsten bronze ceramics

Ferroelectric tantalates with the tetragonal tungsten bronze (TTB) type structure were studied over a wide frequency range from 102 to 109 Hz. Complementary microwave measurements at 36 GHz and micro-Raman experiments were performed in order to extend the dielectric study. A high frequency relaxation was observed above 108 Hz and fitted to the Cole–Cole formula. Different qualitative models are proposed to explain the understanding of the origin of the high frequency relaxation in ferroelectrics. Among these, polar clusters of ferroelectric active off-centred Ta5+ ions are considered

Lattice dynamics and dielectric response of undoped, soft and hard PbZr0.42Ti0.58O3

In this study, ceramic samples of lead zirconate titanate Pb(Zr0.42Ti0.58)O3 (PZT 42/58) doped with Fe (hard) and Nb (soft) were studied by Raman, infrared (IR) and THz spectroscopy in the temperature range from 900 to 20 K. From the evaluation of the IR and Raman phonons in undoped ceramics, we conclude that tetragonal PZT ceramics undergo a low-temperature phase transition to a tilted phase, revealed by anomalies in phonon parameters and the appearance of new modes. Doped samples also presented similar behaviour. The main differences between undoped and doped ceramics lie in the dielectric behaviour below phonon frequency range, where several mechanisms appear: a soft central mode (CM) located near 1 THz and two relaxations in the GHz range. Both types of doping raise the permittivity values below the phonon frequencies, not only increasing the dielectric contribution of the CM, but also modifying the dielectric response near the GHz range. Soft ceramics show higher permittivity with logarithmic increase at low frequencies, corresponding to an almost frequency-independent value of the dielectric losses below 0.1 GHz