Nanoparticle Formation by Laser Ablation and by Spark Discharges — Properties, Mechanisms, and Control Possibilities

Laser ablation (LA) and spark discharge (SD) techniques are commonly used for nanoparticle (NP) formation. The produced NPs have found numerous applications in such areas as electronics, biomedicine, textile production, etc. Previous studies provide us information about the amount of NPs, their size distribution, and possible applications. On one hand, the main advantage of the LA method is in the possibilities of changing laser parameters and background conditions and to ablate materials with complicated stoichiometry. On the other hand, the major advantage of the SD technique is in the possibility of using several facilities in parallel to increase the yield of nanoparticles. To optimize these processes, we consider different stages involved and analyze the resulting plasma and nanoparticle (NP) parameters. Based on the performed calculations, we analyze nanoparticle properties, such as mean size and mean density. The performed analysis (shows how the experimental conditions are connected with the resulted nanoparticle characteristics in agreement with several previous experiments. Cylindrical plasma column expansion and return are shown to govern primary nanoparticle formation in spark discharge, whereas hemispherical shock describes quite well this process for nanosecond laser ablation at atmospheric pressure. In addition, spark discharge leads to the oscillations in plasma properties, whereas monotonous behavior is characteristic for nanosecond laser ablation. Despite the difference in plasma density and time evolutions calculated for both phenomena, after well-defined delays, similar critical nuclei have been shown to be formed by both techniques. This result is attributed to the fact that whereas larger evaporation rate is typical for nanosecond laser ablation, a mixture of vapor and background gas determines the supersaturation in the case of spark

An improved pre-forecasting analysis of electrical loads of pumping station

Relevance of research. In order to reduce energy losses, an accurate and timely forecast of the amount of consumed electricity is necessary. Accurate forecasting of electrical loads of industrial enterprises and their divisions (productions, workshops, departments etc.) allows planning of normal operating conditions, concluding contracts for the electricity supply with the electricity supply company under more favorable conditions, and improving the electricity quality, which ultimately affects the final cost of the products produced by an enterprise. So far, more than 150 forecasting methods of electrical loads have been developed. Usually, the most convenient one is selected based on the forecaster experience by creating and analyzing several forecasting models in order to identify the best. Therefore, in order to simplify the forecasting procedure, it is necessary to develop the methodology for forecasting analysis. This methodology should enable canceling forecasting algorithms that will create lower quality forecasts. The main objective is to develop the methodology for making a forecasting analysis of power consumption on the example of a pumping station of an enterprise with a continuous cycle of work to increase the efficiency of energy consumption and implementation of energy-saving measures. Objects of research: the process of forecasting electrical loads of a pumping station of the enterprise with a continuous cycle of work. Methods of research: fundamental principles of the theory of electrical engineering, statistical methods for power consumption forecasting, the method for detecting the trend of radio signals, and fractal analysis of time series. Research results. The methodology for forecasting analysis of power consumption, which makes it possible to apply the most appropriate methods to forecast the operational power consumption, is developed. For the first time, the radio signal trend detection method is applied to identify the trend of electrical loads. The variation ranges of the fractal parameters of time series of electrical loads are established depending on the variation coefficient of the time series for different periods of time. The Brown method of exponential smoothing that is used to forecast the electrical loads, in the case of identifying the smoothing constant α is in the beyond set ( 1 2 < a < ), is further improved. The regularity of changes in the fractal parameters of time series of power consumption of a pumping station with an increase in the time series duration and their field of application are explained

Effect of Low-Energy Inert-Gas Ion Bombardment of the Metal Surface on the Oxygen Adsorption and Oxidation

It is well known that the metal-surface properties vary as a result of the surface layers ion sputtering in vacuum. This review contains results of the studies of kinetics change of oxygen adsorption and oxidation on the surface of transition metals and alloys in a vacuum during the low-energy (< 10 keV) Ar⁺ ions bombardment. Particularly, the results of the systematic studies of the surface of Cu, Ni, Fe, Co single crystals, and Fe–Ni alloy are presented. The important role of such parameters as a dose of the ion bombarding, ion energy and sample temperature in the chemical activity of surface is noted. It is argued that mechanism of interaction in surface–gas system is substantially controlled by the optimal ratio between the energy and primary ion current density, as well as sputtering rate of natural oxide on the target surface.Хорошо известно, что свойства поверхности металла изменяются в результате ионного распыления поверхностных слоёв в вакууме. Данный обзор содержит результаты исследований изменения кинетики адсорбции кислорода и окисления на поверхности переходных металлов и сплавов в вакууме при бомбардировке ионами Ar⁺ низкой энергии (< 10 кэВ). В частности, приведены результаты систематических исследований поверхности монокристаллов Cu, Ni, Fe, Co и сплава Fe–Ni. Отмечается важная роль таких параметров как доза бомбардировки, энергия ионов и температура образца в изменении химической активности поверхности. Приведены доказательства того, что механизм взаимодействия в системе газ–поверхность существенно контролируется оптимальным соотношением между энергией и плотностью первичного ионного тока, а также скоростью распыления природного оксида на поверхности мишени.Добре відомо, що властивості поверхні металу змінюються в результаті йонного розпорошення поверхневих шарів у вакуумі. Даний огляд містить результати досліджень зміни кінетики адсорбції кисню і окиснення на поверхні перехідних металів і стопів у вакуумі при бомбардуванні йонами Ar⁺ низької енергії (< 10 кеВ). Зокрема, наведено результати систематичних досліджень поверхні монокристалів Cu, Ni, Fe, Co і стопу Fe–Ni. Відзначається важлива роль таких параметрів як доза бомбардування, енергія йонів і температура зразка у зміні хемічної активности поверхні. Наведено докази того, що механізм взаємодії в системі газ–поверхня істотно контролюється оптимальним співвідношенням між енергією та густиною первинного йонного струму, а також швидкістю розпорошення природного оксиду на поверхні мішені

Analysis of compression degree efficiency of schedules of electric loadings

Розглянуто одну з найважливіших переваг вейвлет-аналізу − можливість стиснення інформації. Проведено оцінювання міри стиснення збережених і переданих сигналів залежно від заданої точності. Визначено вплив від використання наведених методик на результати обробки графіків електричних навантажень.In this paper considers one of the important property of wavelet - analysis such as compression of the information. It is made estimation opportunities of compression of stored and transmitted signals depending on setting degrees of accuracy. Influence has determined from usage of the induced techniques of processing on schedules of electric loadings

High-temperature microwave effects in liquid media

The heating behavior of high-boiling liquids under microwave (MW) irradiation was investigated. Linear and non-linear heating modes depending on the applied MW power level were observed. The non-linear interactions emerging at “high” power levels are ascribed to electromagnetic oscillations excitations resulting in non-linear heating speed growth and considerable decrease in energy input. The relationship between non-linearity degree and liquids’ viscosity was established. The observed effects have been shown to apply not only to mere heating, but also to high-temperature chemical reactions. Future perspectives and practical applications of the work are also discussed

Surface composition of the Co-Cr based alloys after different lab denture treatments using auger electron spectroscopy

Метою даної роботи є аналіз хімічного складу поверхні сплаву на основі Co-Cr після декількох технологічних процедур, прийнятих у стоматологічній практиці за допомогою оже-електронної спектроскопії (ОЕС). Цей аналіз проводили після відливання зразків сплавів піддавали наступним послідовним обробкам: розрізанням на алмазному колесі, електроіскровим різанням і шліфуванням, електрополірування, витримки в штучній слині 2 дні після електрополірування