Obtaining the fine-grained silicon carbide, used in the synthesis of construction ceramics

AbstractSilicon carbide is used in the production of construction and temperature-resistant goods, capable of withstanding high mechanical and thermal loads. During recent times, silicon carbide has been frequently used in the electronics industry. Since sintered silicon carbide has increasingly been used as a replacement for metal components of various devices, the process of obtaining compact goods from silicon powder has become the defining factor in the technology used for its synthesis. The selection of conditions in which the sintering is conducted depends on granulometric structure, the form and the surface condition of the initial powder. The work consists of the synthesis of silicon carbide powder using the purified form of metallurgical silicon powder and soot. The qualities of testing samples were studied, where silicon carbide was obtained using established technology, from mechanically activated elementary, fine-grained silicon and soot, by pyrolytic synthesis. It was demonstrated that synthesis produces highly pure silicon carbide powder, (α- and β-phases) with a granulometric composition that allowed subsequent sintering to produce high quality compact goods. It was established that the content of silica in synthesized silicon carbide powder does not exceed 1–2% of the total mass

EEG Correlates of Decision-Making and Preparation of Saccades in Human

A modificated version of experimental scheme "double step" was used to study the decision-making process in saccade programming. Two short visual stimuli were presented sequentially in opposite hemifields (scheme pulse overshoot). The “pattern” of response (double saccade or single saccade at the second target) and latency of the first saccade depended on the duration of the first stimulus (150 or 50 ms). Positive ERP components were revealed within the interval 100 - 120 ms before the saccade onset by using the method of selective EEG averaging. These potentials can be considered as markers of the decision-making process. The parameters and topography of these components indicate involvement of the frontal-parietal neural network of saccadic control and frontal-parietal-and medial-thalamic activation systems of selective attention at the stage of decision-making process

International standards for application of compulsory medical measures

Introduction: The study of the international standards of compulsory medical measures’ (CMM) application to persons who have committed socially dangerous acts is relevant problematics of medical law. The aim: of the research is to define international standards for the implementation of CMM, as well as assessing the state of their implementation in Ukrainian law and medical practice. Materials and methods: The study is based on international acts, ECHR decisions, legislation of Ukraine and foreign countries, scientific articles in the fields of law and psychiatry as well as empirical materials that illustrate application of CMM in Ukraine. Dialectical, comparative-legal, statistical, induction and deduction, legal modeling, sociological research were used in this research. Conclusions: As a result of the research the concept of the international standards of CMM application is defined, their scope in the law-enforcement and medical practice of Ukraine is determined, the system and meaning of these standards are formulated

Propagation of optical femtosecond pulses through quartz and glass ВК-7

In the approximation of dispersion theory to the fourth order inclusive, a theoretical study of the propagation of optical femtosecond pulses of a Gaussian profile and a profile proportional to the hyperbolic secant through quartz and BK-7 glass was carried out. Based on the solutions of the equations for the propagation of pulses of various initial durations through optical materials, dependencies "material length − pulse duration" are obtained. It is shown that, compared with the second approximation of dispersion theory, the fourth approximation gives a slightly lengthy pulse duration. Peculiarities of various time pulse profiles on the pulses duration are also shown. Analytical consideration is confirmed by numerical calculations.Теоретично досліджено проходження оптичних фемтосекундних iмпульсiв гаусового профіля та профіля, пропорцiйного гiперболiчному секансу, через кварц та скло ВК-7 у наближеннi теорії дисперсiї до четвертого порядка включно. На основі рішень рівнянь проходження iмпульсiв рiзної початкової тривалостi через оптичнi матерiали побудовано графiки залежностей «довжина матерiалу – тривалість імпульсу». Показано, що в порівнянні з другим наближенням теорії дисперсії четверте наближення незначно впливає на залежність тривалості імпульсів від довжини оптичного матеріалу. Також показано особливості впливу дисперсії оптичних материіалів на тривалість імпульсів різних часових профілей. Аналітичний розгляд підтверджено чисельними розрахунками.Теоретически исследовано прохождение оптических фемтосекундных импульсов гауссового профиля и профиля, пропорционального гиперболическому секансу, через кварц и стекло ВК-7 в приближении теории дисперсии до четвёртого порядка включительно. На основании решений уравнений прохождения импульсов различной начальной длительности через оптические материалы построены графики зависимостей «длина материала – длительность импульса». Показано, что по сравнению со вторым приближением теории дисперсии четвёртое приближение незначительно влияет на зависимость длительности импульсов от длины оптического материала. Также показаны особенности влияния дисперсии оптических материалов на длительность импульсов различных временных профилей. Аналитическое рассмотрение подтверждено численными расчётами

The high energy cosmic ray particle spectra measurements with the PAMELA calorimeter

Abstract Up until now there has been limited, contradictive data on the high energy range of the cosmic ray electron-positron, proton and helium spectra. Due to the limitations of the use of a magnetic spectrometer, over 8 years experimental data was processed using information from a sampling electro-magnetic calorimeter, a neutron detector and scintillator detectors. The use of these devices allowed us to successfully obtain the high energy cosmic ray particle spectra measurements. The results of this study clarify previous findings and greaten our understanding of the origin of cosmic rays

Deuteron spectrum measurements under radiation belt with PAMELA instrument

Abstract In this work the results of data analysis of the deuteron albedo radiation obtained in the PAMELA experiment are presented. PAMELA is an international space experiment carried out on board of the satellite Resurs DK-1. The high precision detectors allow to register and identify cosmic ray particles in a wide energy range. The albedo deuteron spectrum in the energy range 70 – 600 MeV/nucleon has been measured

PAMELA Observation of the 2012 May 17 GLE Event

The PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment has been collecting data in orbit since July 2006, providing accurate measurements of the energy spectra and composition of the cosmic radiation from a few hundred MeVn up to hundred GeVn. This wide interval of measured energies makes PAMELA a unique instrument for Solar Energetic Particle (SEP) observations. Not only does it span the energy range between the ground-based neutron monitor data and the observations of SEPs from space, but also PAMELA carries out the first direct measurements of the composition for the highest energy SEP events, including those causing Ground Level Enhancements (GLEs). PAMELA has registered many SEP events in solar cycle 24 including the 2012 May 17 GLE event (GLE 71), offering unique opportunities to address the question of high-energy SEP origin. Experimental performances and preliminary results on the 2012 May 17 events will be presented. We will discuss the derived particle injection time and compare with other time scales at the Sun including the flare and CME onset times

Effect of Wind on Soil-Atmosphere Gas Exchange

Global climate change in recent decades is accompanied by rising temperatures and increasing cyclonic activity with strong air flows. How do they affect soil respiration? Is it possible to expect an increase in CO2 emissions and, consequently, a positive feedback of climate change through the greenhouse effect? These questions cannot be answered without the insight into the effect of wind speed on the gas exchange between soil and atmosphere in different landscapes. The paper summarizes the long-term measurements of CO2 efflux from forest-steppe chernozems (Kursk oblast, Russia) in natural and anthropogenic landscapes with forest or herbaceous vegetation depending on wind speed; it presents a physically grounded approach to its quantitative first-approximation (linear) description. The approach assumes an impact of wind through increased forced convection and turbulent diffusivity along with a potential reduction in diffusion mass transfer due to a decrease in the gradient of CO2 concentration between the atmosphere and soil. The constructed inverse parabolic dependence adequately describes the empirical data and assumes a twofold increase in the emission with the wind speed increase to the critical value of 3 m/s and its decreases to the initial level with the further wind speed increase to 6-7 m/s. The intensity of forced convection of soil air turns out to be by five-six orders of magnitude lower than the wind speed in the atmosphere but not inferior to the intensity of conventional isothermal CO2 diffusion, which suggests that this mechanism is to be taken into account in the models of soil-atmosphere gas exchange

Dynamic Analysis of Hydrostatic Transmission with an Axial Flow Divider

Hydrostatic transmission is a system of speed variation of multi-drive vehicle. The use of volumetric flow divider as part of a hydrostatic transmission allows to expand the range of traction and dynamic regulation and to improve the technical characteristics of the vehicle, such as mobility (cross-country ability) and handling. The article presents the dynamic mathematical model of a hydrostatic transmission with a volumetric flow divider that controls the parameters of unadjustable hydraulic motors, and studies its dynamic transient characteristics when the electronic control unit for the pump and flow divider are switched off in the modes of rectilinear movement and maneuvering (turning) of a multi-drive vehicle. The simulation results show that a hydrostatic transmission with a volume flow divider provides effective control of the parameters of motor wheels with unadjustable hydraulic motors