Arcless opening of direct current circuits in technical systems

Operation of the proposed DC circuit breaker consists in the fact that the closing of the thyristor in the DC power circuit with an inductive load results from opening the auxiliary circuit with a current value several fold less than the load current. The power and auxiliary circuits are connected by means of a current transformer having counter switch windings. After switching, the load is shunted by a diode and does not affect the transition process. Simulations and experimental tests of the DC circuit breaker model showed its performance capability, and the breaker can be used for switching in existing DC high current circuits with inductive loads

Thermal Regeneration and Reuse of Carbon and Glass Fibers from Waste Composites

This article aims to develop a method for regenerating and reusing carbon and glass fibers extracted from unrecyclable scraps of carbon plastics, printer parts, and laminating coating. A comparison of known methods of fiber regeneration revealed the advantages of thermal treatment: absence of costs of reagents and complex equipment; better preservation of composition; and strength of fibers. Based on the results of thermographic analysis of wastes in nitrogen and air, the destruction temperatures of their organic matrices were determined (200-460°С), and the use of calcination instead of pyrolysis was justified. The appearance and surface quality of the regenerated fibers are characterized by optical and electron microscopy. It has been established that quantitative extraction of pure carbon and glass fibers from waste crushed to 1 cm is efficient by their calcination at 700 °C for 0.5 h and 500 °C for 1 h, respectively. The principle of creating new composites with the obtained fibers based on the similarity of their composition and binding materials (matrices) has been proposed. It was shown that the introduction of 1 wt% of fibers into slag blocks and active carbon pellets considerably increases their compressive strength, but the bending strength does not change due to dispersed reinforcement. Possible improvement of mechanical properties of products requires reagent treatment of the fiber surface or the introduction of binder additives. Calculations show that the developed method of recycling composite waste can produce 2.3 tons/hour of reinforced building materials that are good for the environment and the economy, excluding expenses for landfill waste disposal and reducing the cost of the product by replacing the primary fiber for the secondary one. Doi: 10.28991/ESJ-2022-06-05-04 Full Text: PD

Effect of benzoyl taurine dipotassium salt on coagulation, hemostasis and vascular activity in the microvasculature of the brain in violation of cerebral circulation

Cerebral circulation disorders (CCD) are one of the most common causes of mortality and disability in the population. Improving the microcirculation of brain tissue is one of the main directions in the treatment and prevention of CCD.Aim of the study was to evaluate the effect of a new derivative of hydroxybenzoic (salicylic) acid on neurological deficit, hemostasis and functional state of arterial pial vessels in the study of prostacyclin-synthetic activity and evaluation of NOmediated endothelial dysfunction in rats under experimental CCD conditions. Material and methods. The experiment was carried out on 50 Wistar rats, which were simulated for CCD by occlusion of common carotid arteries. Within 7 days after the operation, the animals received treatment according to the group: saline, C-60 (N-(3-hydroxybenzoyl)taurine dipotassium salt) and acetylsalicylic acid. After treatment, the activity of the prostacyclin-synthetic system was assessed by the reaction of pial vessels to indomethacin, endothelial dysfunction was estimated by tests with acetylcholine and L-NAME. The parameters of plasma and platelet hemostasis were also studied, and behavioral tests (open field, adhesion test, rotarod, Morris water maze, passive avoidance task) were used to assess neurological deficits in animals. Results. When studying the level of neurological deficit in animals with brain ischemia after a course of administration of the test compound, it was noted that in the treated groups, compared with the control group, there was a significant increase in motor and exploratory activity, improvement in sensory-motor function and coordination of movements (p < 0.05). Also, in the group treated with the salicylic acid derivative, normalization of the parameters of platelet and plasma hemostasis, improvement of the functional state of the vascular endothelium was observed. According to the results of assessing the prostacyclin-synthesizing activity of the endothelium of the cerebral vessels, it follows that the test compound inhibits cyclooxygenase at a level comparable with effect of acetylsalicylic acid. Conclusions. A new derivative of salicylic acid, the dipotassium salt of N-(3-hydroxybenzoyl)taurine, reduces the severity of neurological deficit, improves hemostasis parameters and the functional state of cerebral vessels in rats with brain ischemia in the experiment

A breaker of high current dc circuits with inductive load

The urgency of the discussed issue is caused by the necessi ty of applying different types of switching and principles of construction of switching devices, performing multiple tripping in DC circuits with inductive load. The main aim of the study: to justify the use of the proposed model contactless switch in DC circuits with inductive load performing arcless switching. The methods used in the study: a mathematical model for calculating the transition process, which allows calculating the current in high-current circuit of the used parameters of contactless switch. The results: the authors introduced the model of contactless switch in DC circuits with inductive load. A mathematical model for calculating the transients by the method of state variables has been developed. It allows calculating the current in the load circuit using parameters of contactless switch. The authors held as well the mathematical and the virtual modeling of operation of the model with the given parameters of contactless switch

Possibility of application of inductance-capacitance oscillator in electrochydraulic source of seismic vibrations

The relevance of the research is caused by the need to develop new sources of powerful current pulses for creation of seismic waves in non-explosive seismic exploration. The aim of the research is to carry out estimated and pilot investigations of operation of inductance-capacitance oscillator model using the generalized laws of switching for receiving current pulses in the resistive load. Objects: laboratory model of the inductance-capacitance oscillator with inductively connected inductance coils for increasing current pulse power and steepness in linear active loading. Methods: method of state-space variables for calculating the equations of transient phenomenon in a circuit after switching which are worked out under Kirchhoff's laws, application of the generalized laws of switching for calculating the starting values of currents in the inductance coils and in load resistance. Results. The authors have designed the diagram of the inductance-capacitance oscillator which uses the generalized laws of switching for receiving power current pulses in the resistive load. The oscillator contains the inductive and connected coils that allow increasing the reserved energy and power of the received pulses. Using the method of state-space variables, the mathematical model of operation of the diagram on the linear resistive load was obtained. The authors performed the estimation and pilot researches of the diagram laboratory model. The experimental values of currents in inductance coils and in loading coincided approximately with the calculated ones. Duration of the received current pulses in loading and steepness of the forward front of current pulses make perspective the application of the inductance-capacitance oscillator in seismic exploration, as a source of seismic waves at explosion of a delay

Possibility of application of inductance-capacitance oscillator in electrochydraulic source of seismic vibrations

Актуальность исследования обусловлена необходимостью разработки новых источников мощных импульсов тока для работы на электрогидравлический излучатель, который может применяться для возбуждения сейсмических волн в невзрывной сейсморазведке. Цель: провести расчетные и экспериментальные исследования работы модели индуктивно-импульсного генератора, использующего обобщенные законы коммутации для получения импульсов тока в активной нагрузке; изучить влияние индуктивной связи катушек на амплитуду и крутизну импульсов тока. Объекты: лабораторная модель индуктивно-импульсного генератора, имеющего индуктивно связанные катушки индуктивности для увеличения мощности и крутизны импульса тока в линейной активной нагрузке. Методы: метод переменных состояния для расчета уравнений переходного процесса в цепи после коммутации, составленных по законам Кирхгофа, применение обобщенных законов коммутации для расчета начальных значений токов в катушках индуктивностей и в нагрузке. Результаты. Разработана схема индуктивно-импульсного генератора, использующего обобщенные законы коммутации для получения мощных импульсов тока в активной нагрузке. Генератор содержит индуктивно-связанные катушки, что позволяет увеличить запасаемую энергию и мощность получаемых импульсов. С помощью метода переменных состояния получена математическая модель работы схемы на линейную активную нагрузку. Проведены расчетные и экспериментальные исследования лабораторной модели схемы. Экспериментальные значения токов в катушках индуктивностей и в нагрузке примерно совпали с расчетными значениями. Длительность полученных импульсов тока в нагрузке и крутизна переднего фронта импульсов тока делают перспективным применение индуктивно-импульсного генератора в сейсморазведке в качестве источника импульсов тока в электрогидравлическом излучателе при работе на взрывающуюся проволочку.The relevance of the research is caused by the need to develop new sources of powerful current pulses for creation of seismic waves in non-explosive seismic exploration. The aim of the research is to carry out estimated and pilot investigations of operation of inductance-capacitance oscillator model using the generalized laws of switching for receiving current pulses in the resistive load. Objects: laboratory model of the inductance-capacitance oscillator with inductively connected inductance coils for increasing current pulse power and steepness in linear active loading. Methods: method of state-space variables for calculating the equations of transient phenomenon in a circuit after switching which are worked out under Kirchhoff's laws, application of the generalized laws of switching for calculating the starting values of currents in the inductance coils and in load resistance. Results. The authors have designed the diagram of the inductance-capacitance oscillator which uses the generalized laws of switching for receiving power current pulses in the resistive load. The oscillator contains the inductive and connected coils that allow increasing the reserved energy and power of the received pulses. Using the method of state-space variables, the mathematical model of operation of the diagram on the linear resistive load was obtained. The authors performed the estimation and pilot researches of the diagram laboratory model. The experimental values of currents in inductance coils and in loading coincided approximately with the calculated ones. Duration of the received current pulses in loading and steepness of the forward front of current pulses make perspective the application of the inductance-capacitance oscillator in seismic exploration, as a source of seismic waves at explosion of a delay

Agonist-induced up-regulation of platelet-activating factor receptor messenger RNA in human monocytes

Platelet-activating factor (PAF) is a potent inflammatory mediator and it actions are mediated via specific cell surface receptors which are coupled to G-proteins. PAF stimulates several functions in monocytes and may modulate the expression of its own receptor. To investigate the possible modulation of PAF receptor mRNA expression Northern blot analysis of total RNA from human monocytes was performed using the cDNA of human leukocyte PAF receptor as a probe. Following the addition of 100 nM PAF, there was a 2.0-fold increase in PAF receptor mRNA at 60 minutes after the stimulation, which was inhibited by pretreatment with the PAF receptor antagonist WEB 2086. This increase returned to control level at 120 and 180 min. The increase of PAF receptor mRNA was statistically significant for 10 nM to 1 μM of PAF, while 100 nM of lysoPAF did not increase PAF receptor mRNA levels. These results suggest that PAF receptor expression can be regulated by PAF itself at the transcriptional level.link_to_subscribed_fulltex

Investigation of operation of a low voltage shock generator in an electrohydraulic device for seismic exploration at small depth

Актуальность исследования обусловлена необходимостью разработки новых источников мощных импульсов тока для работы на электрогидравлический излучатель с раздвигающимися электродами, который может применяться для возбуждения сейсмических волн в невзрывной сейсморазведке. Цель: провести расчетные и экспериментальные исследования работы низковольтного ударного генератора на дугу в воде, инициированную раздвигающимися электродами в режиме одиночных импульсов и при получении серии импульсов давления. Провести оптимизацию параметров ударного генератора и электрогидравлического излучателя с целью получения максимального импульса давления. Объекты: низковольтный ударный генератор, выполненный в габаритах кранового асинхронного двигателя МТН-612, подключенный к электрогидравлическому излучателю с раздвигающимися электродами. Методы: согласование параметров ударного генератора и дугового разряда методом планирования эксперимента с помощью математической модели. Результаты. Проведены лабораторные исследования работы низковольтного ударного генератора на дугу в воде, инициированную раздвигающимися электродами в режиме одиночных импульсов и при получении серии импульсов. Методом планирования эксперимента получена математическая модель работы ударного генератора на дугу в воде, инициированную раздвигающимися электродами в режиме одиночных импульсов, получены уравнения регрессии для выходных параметров дугового разряда, проведена оптимизация параметров ударного генератора и электрогидравлического излучателя, что позволяет получить максимальный импульс давления для проведения малоглубинной сейсморазведки. Полученный амплитудно-частотный спектр импульса давления показал, что основная энергия импульса давления лежит в среднечастотном диапазоне от 50 до 100 Гц, что обеспечивает высокий сейсмический КПД для проведения малоглубинной сейсморазведки.The relevance of the study is caused by the need to develop new sources of powerful current pulses for operation in an electrohydraulic device with moving electrodes that can be used to excite seismic waves in non-explosive seismic surveys. The aim of the research is to carry out computational and experimental studies of operation of a low-voltage shock generator on an arc in water, initiated by moving electrodes in the mode of single pulses and in production of a series of pressure pulses. Optimization of the parameters of the shock generator and the electrohydraulic radiator, in order to obtain the maximum pressure pulse. Objects: low-voltage shock generator, made in the dimensions of the crane asynchronous motor MTН-612, connected to an electrohydraulic source with moving electrodes. Methods: matching parameters of a shock generator and an arc discharge by the method of experiment planning using a mathematical model. Results. The authors have carried out the laboratory studies of operation of a low-voltage shock generator on an arc in water initiated by moving electrodes in the regime of single pulses and in the generation of a series of pulses. Using the method of experiment planning, the authors obtained the mathematical model of the shock generator operation on an arc in water, initiated by moving electrodes in the regime of single pulses; the regression equations are obtained for output parameters of the arc discharge. Optimization of the parameters of the shock generator and the electrohydraulic source was carried out, which allows obtaining the maximum pressure pulse for seismic exploration at shallow depth. The obtained amplitude-frequency spectrum of the pressure pulse showed that the main energy of the pressure pulse lies in the low-frequency range from 0 to 180 Hz, which provides a high seismic efficiency for seismic exploration at shallow depth