DEVELOPMENT OF A MODEL FOR THE PRODUCTION OF METAL-POWDER COMPOSITIONS BASED ON CO-CR ALLOYS BY ELECTROEROSIVE DISPERSION

Abstract. The main requirement for powders for additive 3d technologies is the spherical shape of theparticles. Such particles are most compactly packed into a certain volume and ensure the "fluidity" of the powder composition in the supply systems of the material with minimal resistance. The wide use of the EED method for processing metal waste into powders for the purpose of their reuse and application in additive technologies is hampered by the lack in the scientific and technical literature of full-fledged information on the effect of the initial composition, regimes and media on the properties of powders and technologies of practical application. Therefore, in order to develop technologies for the reuse of electroerosive powders and to evaluate the effectiveness of their use, complex theoretical and experimental studies are required. The aim of the work was to develop a model for the production of metal powder compositions on the basis of Co-Cr alloys by electroerosive dispersion. Based on the results of the conducted studies, it has been established that the optimum parameters for the process of obtaining powder materials by the method of electroerosive dispersion of butyl alcohol are: capacitance of discharge capacitors 48 μF, voltage on electrodes 100 V, repetition rate of pulses 120 Hz

Subterahertz chaos generation by coupling a superlattice to a linear resonator

We investigate the effects of a linear resonator on the high-frequency dynamics of electrons in devices exhibiting negative differential conductance. We show that the resonator strongly affects both the dc and ac transport characteristics of the device, inducing quasiperiodic and high-frequency chaotic current oscillations. The theoretical findings are confirmed by experimental measurements of a GaAs=AlAs miniband semiconductor superlattice coupled to a linear microstrip resonator. Our results are applicable to other active solid state devices and provide a generic approach for developing modern chaos-based high-frequency technologies including broadband chaotic wireless communication and superfast random-number generation

Bloch gain in dc-ac-driven semiconductor superlattices in the absence of electric domains

We study theoretically the feasibility of amplification and generation of terahertz radiation in dc-ac-driven semiconductor superlattices in the absence of electric domains. We find that if in addition to dc bias a strong THz pump field is applied, Bloch gain profile for a small THz signal can be achieved under conditions of positive static differential conductivity. Here the positive differential conductivity arises, similarly to the case of large-signal amplification scheme [H. Kroemer, cond-mat/0009311)], due to modifications of dc current density caused by the application of high-frequency ac field [K. Unterrainer \textit{et al.}, Phys. Rev. Lett. \textbf{76}, 2973 (1996)]. Whereas the sign of absorption at low and zero frequencies is sensitive to the ac fields, the gain profile in the vicinity of gain maximum is robust. We suggest to use this ac-induced effect in a starter for THz Bloch oscillator. Our analysis demonstrates that the application of a short THz pulse to a superlattice allows to suppress the undesirable formation of electric domains and reach a sustained large-amplitude operation of the dc-biased Bloch scillator.Comment: 13 pages, 12 figure

DIRECT MAGNETOELECTRIC EFFECT IN TWO-LAYER CERAMIC COMPOSITES BASED ON MANGANESE ZINC FERRITE AND LEAD ZIRCONATE TITANATE

Under different experimental conditions, the direct magnetoelectric effect was studied in two-layer ceramic composites based on manganese zinc ferrite and lead zirconate titanate.Работа выполнена при финансовой поддержке проекта РНФ № 17-72-20105

Study of total antioxidant capacity of red raspberry (Rubus idaeous L.) shoots

BACKGROUND: Today, cardiovascular, oncological, and neurodegenerative diseases are the main causes of death in the world, according to official World Health Organization (WHO) statistics. Antioxidants are used to treat and prevent these diseases. In order to develop optimal technology for obtaining drugs based on plant extracts with antioxidant action, it is necessary to determine the total antioxidant capacity of raspberry shoots. OBJECTIVES: The study aimed to determine the total antioxidant capacity of red raspberry shoots, study the content of biologically active substances (BAS), and the antioxidant activity of red raspberry shoot extracts obtained during subsequent exhaustive extraction. METHODS: The number of phenolic compounds, catechins, flavonoids, and hydroxycinnamic acids was determined by a spectrophotometric analysis method, whereas organic acids were determined by the alkalimetric method in red raspberry shoot extracts; the antioxidant activity of obtained extracts was evaluated by potentiometric method. RESULTS:  The total antioxidant capacity of red raspberry shoots was 164.12 mmol-equiv./m dry weight, the sum of the total content of phenolic compounds was 24.40 mg gallic acid (GA)/mL, catechins – 21.36 mg epigallocatechin-3-O-gallate (EGCG)/mL, flavonoids – 0.77 mg rutin (R)/mL, hydroxycinnamic acids derivatives – 2.56 mg chlorogenic acid (ChA)/mL and organic acids – 1.88 mg citric acid (CA)/mL in red raspberry shoot extracts obtained during subsequent exhaustive extraction. The analysis showed that there is a very high positive correlation between antioxidant activity and total phenolic compounds, catechin, flavonoid, hydroxycinnamic acids derivatives, and organic acids content in red raspberry shoot extracts. CONCLUSIONS: Total red raspberry shoots' antioxidant capacity has been determined. The study results can be used to develop optimal technology for obtaining drugs based on the extract of red raspberry shoots, which has an antioxidant effect

Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field

We report on the observation and experimental studies of impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field. The terahertz electroluminescence is observed in a wide range of doping levels (at noncompensated donor density from 4.5×10[sup 16] to 3.4×10[sup 18] cm[sup −3]). Spectra of terahertz luminescence and photoconductivity are studied by means of Fourier transform spectrometry. Distinctive features of the spectra can be assigned to intracenter electron transitions between excited and ground states of silicon and oxygen donors and to hot electron transitions to the donor states.Peer reviewe

Poloidal inhomogeneity of the particle fluctuation induced fluxes near of the LCFS at lower hybrid heating and improved confinement transition at the FT-2 tokamak

This paper deals with the new spectral and microturbulence experimental data and their analysis, which show, that the radial electric field Er generated at the LH heating (LHH) in the FT-2 is high enough to form the transport barriers. The ETB is formed when LHH is switched off. The radial fluctuation-induced EB drift flux densities near LCFS in SOL are measured at two different poloidal angles. For this purpose two Langmuir probes located at low and high field sides of the torus are used. Registration of the poloidal and radial components of the electric field and density fluctuations at the same time during one discharge permits to measure the poloidal asymmetry of the transport reduction mechanism of the radial and poloidal particle fluxes in the SOL. The absolute E(~) fluctuation levels show dependence on the sign of Er shear. The modification of the microscale turbulence by the poloidal Er x B rotation shear EB at the L - H transition near LCFS is also studied by X-mode fluctuation Reflectometry. The new data were obtained by spatial spectroscopic technique.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France