Instruments and Experimental Techniques最新文献

Studying the aeration regime under urban conditions is an important and urgent task. The main research approaches in its solution are numerical modeling and experiments in wind tunnels. Experimental data are important both for a qualitative assessment of the flow structure and for verifying mathematical models. This paper presents the results of studies of surface vortex structures using the oil-film visualization method for models of various types of urban development carried out at aerodynamic installations. A method for conducting the experiment is described both on canonical cube-shaped models and for more complex building layouts. A comparison of the results of oil-film visualization with the calculated vector stress fields on the surface showed their qualitative compliance.

The article considers the principles of constructing a high-voltage source with an output voltage of 50–200 kV for powering a linear electrostatic accelerator of dust particles, which is used to simulate the impact of micrometeoroids and space debris on the structural elements of spacecrafts. Based on computer modeling, the main electronic components included in the high-voltage generator circuit were selected and were tested as part of the accelerator. The effect of output voltage pulsations on the acceleration of a dust particle with dimensions of 1–10 μm in the path consisting of 11 hollow cylindrical electrodes with a total accelerating voltage of 100 kV was calculated.

The fluxes of thermal and resonance neutrons, the dependence of neutron flux on energy, and the resolution function were determined experimentally for the 11- and 60-m flight paths (channels 3 and 4) of the intense resonance neutron source (IREN) facility at the Joint Institute for Nuclear Research Russia (JINR). The experimentally obtained characteristics of the IREN facility were confirmed by Monte Carlo calculations.

This paper presents the development of a piezo-driven calibration device for force sensors. A piezoelectric actuator is used to generate the original driving force, and a two-stage hybrid displacement amplifier can adjust the driving displacement and loaded force into the desirable range for sensor calibration. A force tester is set on the output end of the amplifier to load and monitor the calibration force. The features of the displacement amplifier and force tester are theoretically modeled and verified by finite element analysis (FEA). A laboratorial prototype is realized by assembling the commercial piezoelectric actuator into the displacement amplifier fabricated using wire electrical discharge machining and adhering metallic strain gauge onto the sensing beam of the force tester. The experimental results demonstrate that the device can output a displacement of 666 μm under the 130 V driving voltage and successfully realize the 0.2 N-range sensor calibration with the error of 0.56%.

A code has been developed for simulating the propagation and absorption of fast magnetosonic (FMS) waves excited in plasmas of controlled-fusion facilities. The longitudinal and azimuthal wavenumbers of an FMS wave propagating in a deuterium plasma with parameters characteristic of the ohmic-heating regime in the L-2M stellarator have been calculated. The wave frequency corresponds to the second harmonic of the ion cyclotron frequency of deuterium. The model of cold collisionless cylindrical plasma is used. The FMS wave absorption by ions and electrons has been calculated. It is shown that, for the second harmonic of the ion cyclotron frequency, 79% of the FMS wave power will be absorbed by ions. Therefore, in deuterium plasma, for efficient current drive using FMS waves, it is necessary either to use higher harmonics of the ion cyclotron frequency or to search for alternative mechanisms of FMS wave absorption by electrons, e.g., the mode conversion current drive method.

As a potential cartilage substitute, the research on the mechanical properties of hydrogel is crucial. Addressing the issue of traditional hydrogel compression devices' inability to maintain compatibility with cell culture environments, a multi-channel bionic exciter incorporating a six-unit indenter structure was developed in this study. The system integrates high-accuracy linear motors (with the position resolution of 0.002 mm) and force transducers (with the accuracy of ±0.01 N) to provide dynamic mechanical stimulation while recording real-time load-displacement data. This instrument enables compression experiments of hydrogels to be conducted under standard cell culture conditions. Experimental validation demonstrated that the instrument was able to accurately simulate predefined mechanical stimuli and record real-time data. This provides a reliable platform for investigating the effects of cyclic mechanical stimulation on hydrogel-mediated cell behavior regulation, it holds significant value for the study of mechanical properties of hydrogels and other biomaterials.

An automatic meter of pulsed or continuous light fluxes is controlled by a central processor. The gain is regulated by two digital potentiometers, and a control method is proposed. When the light flux increases to Φ_max = 2.2 × 10⁻⁵ W, it is possible that Reduce light flux command is produced. The meter sensitivity is increased by a synchronous detector. The sensitivity characterized by the pulsed power at a wavelength of 520 nm is 0.1 × 10⁻⁶ W or better. The modulation frequency of the light flux is 1000 Hz. Formulas are provided for switching to a different modulation frequency.

A description is given of an instrument complex for measuring spectral underwater illumination at different depths of freshwater reservoirs, which consists of two sealed submersible measuring boxes and one external data-processing unit. The main difference between the complex and similar devices is the minimization of the impact of changes in external surface illumination associated with clouds, fog, haze, and weak surface waves on measurements. The complex was tested at various depths in several areas of Lake Teletskoye during an expedition in summer 2024. The results of measurements are presented and the impact of weak waves on the water surface is assessed.

The specialized MASI-USB scanner is used for optical measurements and analysis of the shape and structure of supersonic underexpanded gas jets with a complex shape in a rarefied medium with the pressure of 0.2–20 Pa. The gas glow was initiated by a focused electron beam with the energy of approximately 10 keV. The sections of the gas jet are obtained by the uniform displacement of the jet relative to the electron beam. The possibilities of using a scanning system developed on the basis of modern hardware and software to visualize flows in supersonic jets with a complex flow configuration are demonstrated. The combination of scanning and photo-visualization provides an opportunity for a more complete description of the structure of supersonic flows, including those in the conditions of clustered flows.

The methodological approaches to determining the parameters of radiation-defect annealing and, therefore, the stored-energy release (the Wigner energy) are presented. The methods for graphite sampling from various locations and elements of graphite stacks of industrial graphite-moderated uranium reactors are considered. The design of an experimental setup for differential thermal analysis of samples is described. By using this setup, it is possible to obtain the Wigner energy release spectra of graphite and to test the algorithm of their mathematical processing for determining the activation energies.