Application Of Rf (13.56 MHz) Arc Discharge For Plasma Chemical Conversion Of Volatile Fluorides

The report discusses the use of a new type of plasma source of hydrogen plasma based on a RF (13.56 MHz) arc discharge of atmospheric pressure between two electrodes. This discharge was used for hydrogen reduction of the tetrafluorides of silicon, boron and molybdenum. As a result of the studies, the main regularities of the hydrogen reduction process were established and the main synthesized products were determined. Samples of carbides of silicon, boron and molybdenum were prepared

Application of RF (13.56 MHz) Arc Discharge for Plasma Chemical Conversion of Volatile Chlorides of Silicon and Germanium.

The processes of hydrogen reduction of silicon and germanium chlorides are studied under RF conditions (40.68 MHz) of contracted atmospheric pressure arc discharge stabilized between two rod electrodes. The main gas-phase and solid products of plasma-chemical transformations are determined. Using the hydrogen reduction of SiCl4 as an example, the numerical simulation of gas-dynamic and heat exchange processes for this type of discharge was performed. The studies were carried out for the optimal conditions for obtaining trichlorosilane using modern computational technologies of fluid dynamics which made it possible to detail the velocity and temperature fields, the gas flow rates in the plasma region, and also determine the main temperature zones affecting the hydrogen reduction process

Phase diagram of Pb(Zr,Ti)O3 solid solutions from first principles

A first-principles-derived scheme, that incorporates ferroelectric and antiferrodistortive degrees of freedom, is developed to study finite-temperature properties of PbZr1-xTixO3 solid solutions near its morphotropic phase boundary. The use of this numerical technique (i) resolves controversies about the monoclinic ground-state for some Ti compositions, (ii) leads to the discovery of an overlooked phase, and (iii) yields three multiphase points, that are each associated with four phases. Additional neutron diffraction measurements strongly support some of these predictions.Comment: 10 pages, 2 figure

Structural and physical determinants of the proboscis-sucking pump complex in the evolution of fluid-feeding insects

© 2017 The Author(s). Fluid-feeding insects have evolved a unique strategy to distribute the labor between a liquid-acquisition device (proboscis) and a sucking pump. We theoretically examined physical constraints associated with coupling of the proboscis and sucking pump into a united functional organ. Classification of fluid feeders with respect to the mechanism of energy dissipation is given by using only two dimensionless parameters that depend on the length and diameter of the proboscis food canal, maximum expansion of the sucking pump chamber, and chamber size. Five species of Lepidoptera - White-headed prominent moth (Symmerista albifrons), White-dotted prominent moth (Nadata gibosa), Monarch butterfly (Danaus plexippus), Carolina sphinx moth (Manduca sexta), and Death's head sphinx moth (Acherontia atropos) - were used to illustrate this classification. The results provide a rationale for categorizing fluid-feeding insects into two groups, depending on whether muscular energy is spent on moving fluid through the proboscis or through the pump. These findings are relevant to understanding energetic costs of evolutionary elaboration and reduction of the mouthparts and insect diversification through development of new habits by fluid-feeding insects in general and by Lepidoptera in particular

A combined theoretical and experimental study of the low temperature properties of BaZrO3

Low temperature properties of BaZrO3 are revealed by combining experimental techniques (X-ray diffraction, neutron scattering and dielectric measurements) with theoretical first-principles-based methods (total energy and linear response calculations within density functional theory, and effective Hamiltonian approaches incorporating/neglecting zero-point phonon vibrations). Unlike most of the perovskite systems, BaZrO3 does not undergo any (long-range-order) structural phase transition and thus remains cubic and paraelectric down to 2 K, even when neglecting zero-point phonon vibrations. On the other hand, these latter pure quantum effects lead to a negligible thermal dependency of the cubic lattice parameter below ~ 40 K. They also affect the dielectricity of BaZrO3 by inducing an overall saturation of the real part of the dielectric response, for temperatures below ~ 40 K. Two fine structures in the real part, as well as in the imaginary part, of dielectric response are further observed around 50-65 K and 15 K, respectively. Microscopic origins (e.g., unavoidable defects and oxygen octahedra rotation occurring at a local scale) of such anomalies are suggested. Finally, possible reasons for the facts that some of these dielectric anomalies have not been previously reported in the better studied KTaO3 and SrTiO3 incipient ferroelectrics are also discussed.Comment: 8 pages, 5 figures, submitted to Physical Review

Gravitational oscillations of a liquid column

We report gravity oscillations of a liquid column partially immersed in a bath of liquid. We stress in particular some peculiarities of this system, namely (i) the fact that the mass of this oscillator constantly changes with time; (ii) the singular character of the beginning of the rise, for which the mass of the oscillator is zero; (iii) the sources of dissipation in this system, which is found to be dominated at low viscosity by the entrance (or exit) effects, leading to a long-range damping of the oscillations. We conclude with some qualitative description of a second-order phenomenon, namely the eruption of a jet at the beginning of the rise.Comment: 22 pages, pdf. Submitted to Physics of Fluid

Многоуровневый вейвлет анализ в задаче сегментации электрокардиограмм

Пропонується алгоритм сегментації електрокардіограм (ЕКГ) з використанням багаторівневого вейвлет аналізу сигналів. Алгоритм був протестований, на прикладах кардіограм, що були взяті з міжнародної бази даних електрокардіограм MIT-BIH Arrhythmia Database. Тестовий матеріал має широкий набір форм: нормальні та патологічні сигнали, сигнали, ускладнені шумами різних частот та потужностей. Точність локалізації QRS комплексу ЕКГ складає 98%, точки J – 95%, T зубця – 86%, P зубця – 80%.This article proposes an electrocardiogram (ECG) segmentation algorithm, using multi-resolution wavelet analysis of signals. The algorithm was tested using ECG taken from international electrocardiogram databases: MIT-BIH Arrhythmia Database. Test material has a wide range: normal and pathological signals, signals, complicated by noise of different frequencies and capacities. Accuracy of ECG QRS complex localization is 98%, the point J - 95%, T wave - 86%, P wave - 80%.Предлагается алгоритм сегментации электрокардиограмм (ЭКГ) с использованием многоуровневого вейвлет анализа сигналов. Алгоритм был протестирован на примерах кардиограмм, которые были взяты из международной базы данных электрокардиограмм MIT-BIH Arrhythmia Database. Тестовый материал имеет широкий набор форм: нормальные и патологические сигналы, сигналы, осложненные шумами различных частот и мощностей. Точность локализации QRS комплекса ЭКГ составляет 98%, точки J - 95%, T зубца - 86%, P зубца - 80%

Coexistence of Ferroelectric Triclinic Phases and Origin of Large Piezoelectric Responses in Highly Strained BiFeO3 films

The structural evolution of the strain-driven morphotropic phase boundary (MPB) in BiFeO3 films has been investigated using synchrotron x-ray diffractometry in conjunction with scanning probe microscopy. Our results demonstrate the existence of mixed-phase regions that are mainly made up of two heavily tilted ferroelectric triclinic phases. Analysis of first-principles computations suggests that these two triclinic phases originate from a phase separation of a single monoclinic state accompanied by elastic matching between the phase-separated states. These first-principle calculations further reveal that the intrinsic piezoelectric response of these two low-symmetry triclinic phases is not significantly large, which thus implies that the ease of phase transition between these two energetically close triclinic phases is likely responsible for the large piezoelectric response found in the BiFeO3 films near its MPB. These findings not only enrich the understandings of the lattice and domain structure of epitaxial BiFeO3 films but may also shed some light on the origin of enhanced piezoelectric response near MPB.Comment: 19 pages, 3 figures and 1 tabl