Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes

Numerical Cherenkov radiation (NCR) or instability is a detrimental effect frequently found in electromagnetic particle-in-cell (EM-PIC) simulations involving relativistic plasma beams. NCR is caused by spurious coupling between electromagnetic-field modes and multiple beam resonances. This coupling may result from the slow down of poorly-resolved waves due to numerical (grid) dispersion and from aliasing mechanisms. NCR has been studied in the past for finite-difference-based EM-PIC algorithms on regular (structured) meshes with rectangular elements. In this work, we extend the analysis of NCR to finite-element-based EM-PIC algorithms implemented on unstructured meshes. The influence of different mesh element shapes and mesh layouts on NCR is studied. Analytic predictions are compared against results from finite-element-based EM-PIC simulations of relativistic plasma beams on various mesh types.Comment: 31 pages, 20 figure

Study of Combined Cleaning Process of Sunroot Tubers

Elaboration and improvement of the process of raw material cleaning is an urgent scientifically technical process. The one of most prospective directions of vegetables cleaning process intensification is the elaboration of combined methods of their cleaning. The improvement of tubers cleaning process is based on the combination of thermal processing of sunroot tubers by steam and the process of further mechanical additional cleaning.The experimental studies of the influence of parameters of the process of sunroot thermal processing by steam on a tuber surface layer transformation were carried out. The influence of the steam pressure and the duration of the process of tubers thermal processing on the depth of the thermal processing of tuber surface layer and also on the effectiveness of the peel separation were studied. At the same time there were realized the studies as to the influence of the duration of tubers mechanical additional cleaning process on cleaning quality parameters. The experimental apparatus and correspondent method that allow to carry out investigations of the combined process of sunroot tubers cleaning with a possibility to determine the influence of all its parameters on the percent of raw material losses and cleaning quality were elaborated. Rational regimes of the combined process of sunroot tubers cleaning were established

Investigation of the Application of a New Method of Extraction Intensification of Pectin Substances From a Beet Pulp

The aim of research is studying a new method for intensifying extraction of pectin substances during acid extraction of pectin-containing raw materials. The description of the experimental setup and the procedure for processing the results of the investigation of the application of a new method for intensifying the beet pulp extraction are described. The results of experimental studies on the application of a new combined mixing element for intensifying the extraction of pectin-containing raw materials (beet pulp) and its effect on quantitative and qualitative output characteristics are presented. Mathematical models are constructed on the basis of regression equations of the full factorial experiment with the use of a new method of intensifying the extraction process to select input technological parameters for the extraction of pectin substances from pectin-containing raw materials. The rational operating parameters of the process of extraction of pectin substances with the use of a new combinable stirring element are determined. Such working parameters are: the process duration is 1 ... 1.1, the temperature of the working medium is 60 ... 70 ºС, and the hydromodule is 8 ... 10. The research results can be used to study other technological parameters of the extraction process of pectin substances, as well as to develop a technological line for the production of pectin products

Спектральная эллипсометрия как метод изучения влияния быстрой термообработки кремниевых пластин на их оптические характеристики

One of the possible ways of improvement of the surface properties of silicon is the solid phase recrystallization of the surface silicon layer after the chemical-mechanical polishing with application of the rapid thermal treatment with the pulses of second duration. The purpose of the given paper is investigation of influence of the rapid thermal treatment of the initial silicon wafers of the various doping level and reticular density on their optical characteristics by means of the spectral ellipsometry method.The investigation results are presented by means of the spectral ellipsometry method of the rapid thermal processing influence on the initial silicon wafers (KDB12 orientation <100>, KDB10 orientation <111> and KDB0.005 orientation <100>) of the various level of doping and reticular density influence on their optical characteristics: refraction and absorption ratios. Influence was confirmed of the silicon reticular density on its optical characteristics before and after the rapid thermal processing. It was shown, that reduction of the refraction and absorption ratios in the center of the Brillouin zone for the silicon samples with the high Boron concentration after the rapid thermal processing as compared with the low doped silicon. In the area of the maximum absorption peak, corresponding to the energy of the electron exit from the silicon surface (4.34 eV) the refraction indicator of the high doped silicon becomes higher, than of the low doped silicon, which is determined by the high concentration of the vacant charge carriers on the silicon surface in this spectral range.It was established, that the spectral area 3.59–4.67 eV, corresponding to the work of the electrons, exiting the silicon surface, the most informative way shows the difference of the 3 optical parameters of silicon of the different orientation, and for evaluation of influence of the silicon doping level on its optical characteristics the most informative is the spectral range of 3.32–4.34 eV. Одним из возможных путей улучшения поверхностных свойств кремния является твердофазная рекристаллизация поверхностного слоя кремния после химико-механической полировки с использованием быстрой термической обработки импульсами секундной длительности. Целью данной работы являлось исследование влияния быстрой термической обработки исходных кремниевых пластин различного уровня легирования и ретикулярной плотности на их оптические характеристики методом спектральной эллипсометрии.Приведены результаты исследования методом спектральной эллипсометрии влияния быстрой термообработки исходных кремниевых пластин (КДБ-12 ориентации <100>, КДБ-10 ориентации<111> и КДБ-0,005 ориентации <100>) различного уровня легирования и ретикулярной плотности на их оптические характеристики: коэффициенты преломления, поглощения. Подтверждено влияние ретикулярной плотности кремния на его оптические характеристики до и после быстрой термообработки. Установлено уменьшение коэффициентов преломления и поглощения в центре зоны Бриллюэна для образцов кремния с высокой концентрацией бора после быстрой термообработки по сравнению с низколегированным кремнием. В области пика максимума поглощения, соответствующего энергии выхода электрона с поверхности кремния (4.34 эВ) показатель преломления высоколегированного кремния становится выше, чем у низколегированного кремния, что обусловлено высокой концентрацией свободных носителей заряда на поверхности кремния в этом спектральном диапазоне.Установлено, что спектральная область 3.59–4.67 эВ, соответствующая работе выхода электронов с поверхности кремния, наиболее информативно показывает различие оптических параметров кремния различной ориентации, а для оценки влияния уровня легирования кремния на его оптические характеристики наиболее информативен спектральный диапазон 3.32–4.34 эВ

Crustal and Upper Mantle Velocity Model along the DOBRE-4 Profile from North Dobruja to the Central Region of the Ukrainian Shield : 1. Seismic Data

For studying the structure of the lithosphere in southern Ukraine, wide-angle seismic studies that recorded the reflected and refracted waves were carried out under the DOBRE-4 project. The field works were conducted in October 2009. Thirteen chemical shot points spaced 35-50 km apart from each other were implemented with a charge weight varying from 600 to 1000 kg. Overall 230 recording stations with an interval of 2.5 km between them were used. The high quality of the obtained data allowed us to model the velocity section along the profile for P-and S-waves. Seismic modeling was carried out by two methods. Initially, trial-and-error ray tracing using the arrival times of the main reflected and refracted P-and S-phases was conducted. Next, the amplitudes of the recorded phases were analyzed by the finite-difference full waveform method. The resulting velocity model demonstrates a fairly homogeneous structure from the middle to lower crust both in the vertical and horizontal directions. A drastically different situation is observed in the upper crust, where the Vp velocities decrease upwards along the section from 6.35 km/s at a depth of 15-20 km to 5.9-5.8 km/s on the surface of the crystalline basement; in the Neoproterozoic and Paleozoic deposits, it diminishes from 5.15 to 3.80 km/s, and in the Mesozoic layers, it decreases from 2.70 to 2.30 km/s. The sub-crustal Vp gradually increases downwards from 6.50 to 6.7-6.8 km/s at the crustal base, which complicates the problem of separating the middle and lower crust. The Vp velocities above 6.80 km/s have not been revealed even in the lowermost part of the crust, in contrast to the similar profiles in the East European Platform. The Moho is clearly delineated by the velocity contrast of 1.3-1.7 km/s. The alternating pattern of the changes in the Moho depths corresponding to Moho undulations with a wavelength of about 150 km and the amplitude reaching 8 to 17 km is a peculiarity of the velocity model.Peer reviewe

Spectral Ellipsometry as a Method of Investigation of Influence of Rapid Thermal Processing of Silicon Wafers on their Optical Characteristics

One of the possible ways of improvement of the surface properties of silicon is the solid phase recrystallization of the surface silicon layer after the chemical-mechanical polishing with application of the rapid thermal treatment with the pulses of second duration. The purpose of the given paper is investigation of influence of the rapid thermal treatment of the initial silicon wafers of the various doping level and reticular density on their optical characteristics by means of the spectral ellipsometry method. The investigation results are presented by means of the spectral ellipsometry method of the rapid thermal processing influence on the initial silicon wafers (KDB12 orientation , KDB10 orientation and KDB0.005 orientation ) of the various level of doping and reticular density influence on their optical characteristics: refraction and absorption ratios. Influence was confirmed of the silicon reticular density on its optical characteristics before and after the rapid thermal processing. It was shown, that reduction of the refraction and absorption ratios in the center of the Brillouin zone for the silicon samples with the high Boron concentration after the rapid thermal processing as compared with the low doped silicon. In the area of the maximum absorption peak, corresponding to the energy of the electron exit from the silicon surface (4.34 eV) the refraction indicator of the high doped silicon becomes higher, than of the low doped silicon, which is determined by the high concentration of the vacant charge carriers on the silicon surface in this spectral range. It was established, that the spectral area 3.59–4.67 eV, corresponding to the work of the electrons, exiting the silicon surface, the most informative way shows the difference of the 3 optical parameters of silicon of the different orientation, and for evaluation of influence of the silicon doping level on its optical characteristics the most informative is the spectral range of 3.32–4.34 eV

The main groups of adjuvants and the prospects of their use for the specific prevention of particularly dangerous and other infectious diseases

The purpose of this review is to analyze scientific data on the adjuvant properties of substances of various origin and chemical nature (adjuvants) published in recent decades and to evaluate the effectiveness of their use in the vaccination against various infections, including particularly dangerous ones. The analysis of the literature data available in PubMed, Web of Science, Scopus, eLibrary databases, indicates that the search for new substances and drugs with the ability to enhance the immune response to antigens that are part of antibacterial and antiviral registered vaccines, as well as experimental preventive drugs, is an important and promising direction. The use of various substances and compounds as adjuvants enhances the immunogenic and protective properties of vaccines, reduces the antigenic load on the human body and causes a tense immune response in individuals with reduced functioning of immune system and in the elderly. When choosing an adjuvant, it is necessary to take into account the direction of its action on the formation of both local and systemic specific immune response, depending on the nature of the pathogen