Modeling of thermal processes in the contact zones of fuel elements

In this work, using two specific examples, a general approach to the mathematical modeling of thermal processes in the contact zones of fuel elements in the development and optimization of various technological processes, systems and devices is considered. In the first example, a mathematical model of heat transfer in the contact zone (metal-hybrid thermal interface) between the heat-generating element and the heat-dissipating radiator is considered. In the second case, the thermal process in the processing of materials with a bonded diamond tool in the contact zone "diamond grain – binder – processed material" is considered and analyzed. The general approach to modeling thermal processes in the contact zones of various fuel elements makes it possible to optimize the parameters of technological processing modes and the correct operating conditions for products and systems

Measuring complex for determining the characteristics of high-voltage silicon carbide Schottky diodes in impulse modes

This paper describes a developed automated research measuring complex that allows one to determine the parameters of currents, voltages and power of silicon carbide Schottky diodes when applied reverse voltage impulses with amplitudes from 400 to 1000 V. The research measuring complex was tested on DDSH411A91 («GRUPPA KREMNY EL») and C3D1P7060Q (Cree/Wolfspeed) silicon carbide Schottky diodes and allows to determine their maximum values of the rate of rise of reverse voltage dV/dt (877 V/ns and 683 V/ns). Also, the maximum values of the current rise rate dI/dt were determined for DDSH411A91 (3.24 A/ns) and C3D1P7060Q (3.72 A/ns) diodes. For the first time it was established that, when a reverse voltage impulse with an amplitude of 1000 V is applied, the maximum values of instantaneous fullpower reach 1419 VA for the DDSH411A91 diode and 1638 VA for the C3D1P7060Q diode.

Investigation of the dynamics of heating metal-dielectric structures with nanometer conductive film under the influence of microwave fields

The paper presents the results of experimental studies and analysis of the dynamics of heating of metal-dielectric structures (MDS) with aluminum conducting films on glass or sitall substrates when exposed to powerful microwave fields, as well as when exposed to direct and alternating currents.

Ultra-weak emission and microcurrents instabilities in blue GaN LEDs at different stages of degradation

It is found that the ultra-weak luminescence observed in microcurrents mode in blue GaN LEDs with multiple quantum wells is due to tunnel-recombination processes with the participation of defect states and local potential wells of various depths, which arise as a result of planar fluctuations of indium in the InGaN layers of the active region. Digital photographs were obtained and patterns of ultra-weak luminescence of the surface of LED crystals were analyzed. It is shown that the patterns of luminescence, along with the current-voltage characteristic, demonstrate significant changes after testing even at the initial stages of degradation, which indicates a high sensitivity of these parameters to degradation processes and the possibility of their use in diagnostic and non-destructive testing methods.

Application of the optoacoustic effect to measure glucose concentration

Currently, there are only two invasive methods available for measuring blood glucose: the first, the most common method, requires blood to be drawn, which is then transported and analyzed to a clinical laboratory, applying the blood to a glucometer test strip. Sampling blood, especially in children, is a rather complicated process, in addition, the results of clinical trials take time. Therefore, non-invasive, continuous monitoring of glucose by optoacoustic method is quite promising. We used an optoacoustic method with a high spatial resolution, which makes it possible to measure the concentration of glucose in the blood. Experimental measurements were carried out in porcine blood at various glucose concentrations

The properties of AISI 316L steel after surface treatment with Ti surface alloy and a-C:H:SiOx coating

The paper presents the research results of corrosion and mechanical properties of the AISI 316L stainless steel after the surface treatment. This treatment includes the formation of the titanium-based surface alloy provided by the low-energy high-current electron beam. The obtained surface alloy used as an underlayer, is then coated with the a-C:H:SiOx film using the PACVD method. It is shown that such a combined treatment of the steel surface improves its corrosion resistance, i. e., reduces the current density from 110-7 to 910-10 A/cm2 and corrosion rate from 1.110-3 to 9.310-6 mm/year. The resulted modified steel surface possesses high mechanical and tribological properties

Features of the optical medium of the surface of plant seeds

It was found that the integumentary tissue of plant seeds has the property of enhancing luminescence light. This phenomenon manifests itself in both the time and frequency domain. The gain factor (in power), depending on the type of seed, varies from 1.7 (beans) to 2.6 (rye). To determine it, the optical medium of the plant seed surface was represented as a dynamic link having an input and output. The impulse (time) characteristic of the link was found by the relaxation curve of luminescence. The dependence of the gain on temperature is expressed in the fact that when it decreases from 50 oC to –30 oC, the gain increases from 1.73 to 2.48. This phenomenon can be explained by the fact that at the stage of relaxation of luminescence, the absorption coefficient of the optical medium of the seed surface takes a negative value

Study of the influence of diamond-like carbon film deposition technology on the change of its physical and mechanical characteristics

The paper presents the results of testing the technology of deposition of diamond-like carbon films on the surface of stainless steel substrates at different process parameters, a quantitative assessment of the sp3 bond content and the physical and mechanical characteristics of the coatings obtained, a conclusion about the influence of the deposition process technological parameters on these characteristics is formulated.

Calculation of single-layer dielectric coatings for antireflection in a given range of angles of incidence

In this work, the problem of antireflection a single-layer magneto-dielectric system is formulated when a plane electromagnetic wave passes through it in the range of angles of incidence, and necessary and sufficient conditions for the existence of solutions to this problem are obtained

Dependence of the Xe flash lamps’ UV radiation efficiency on the volumetric power density of the discharge

The study results of the peak and average electrical volumetric power density influence on the radiation efficiency and brightness temperature in the 200–300 nm bactericidal spectrum range are presented. A linear dependence of the radiation efficiency change in the 5.1–8.4 % range was obtained with the average volumetric power density increase from 177 to 390 kW/cm3. The brightness temperature dependence in the specified spectral region on the peak volumetric power density is a logarithmic character with decreasing growth rate when approaching 9 kK. This effect can be associated with both radiation blocking by vaporized quartz fumes and with UV light shielding by outer plasma layers