The influence of artificial turbulization on the efficiency of heat exchange in the channels of solar air heating collectors

In this work, the kinetic phenomena of strain-sensitive thin PbTe films with the presence of chlorine are studied. It has been established that when adding a legirant, the concentration of current carriers and the mobility increase 1.9*1020cm-3, Ϭmax = 4959 ohm-1sm-1, respectively. It has been determined that the coefficient of strain sensitivity of polycrystalline PbTe films doped with chlorine reaches up to 35000 in the strain range (1÷8.5)·10-7 rel.un.

Effects of the interaction of chlorine with PbTe surface and their effect kinetic parameters of strain-sensitive films

Otajonov,

Khalilov,

Juraev

et al. 2024

Study and analysis of geometric and dynamic dimensions of segner type jet turbines

Urmonov,

Toxirov,

Boynazarov

et al. 2024

Today, the production of electricity from renewable energy sources is a priority for all countries. Specifically, there is extensive scientific research being conducted on the effective use of small and lowpressure water sources for electricity generation. This research focuses on the creation and improvement of hydropower devices in numerous leading scientific and higher educational institutions worldwide. This article investigates a jet turbine based on a Segner wheel operating in low-pressure water sources. The study examines how the geometric shape and the number of nozzles of a hydraulic turbine affect the speed and pressure changes of a moving water flow at various points. This analysis is performed through mathematical modeling using COMSOL Multiphysics version 6.1 (Build: 282), which employs a standard RANS method for nozzles of five different geometric shapes in the CFD module, specifically in the Turbulent Flow, k- ε model. To determine the optimal geometric shape of the nozzle, the study divided the water at the nozzle inlet into water bundles. Triangles were formed based on the impact direction of each water clot on the nozzle's inner walls, directed toward the center of the outlet. These were determined by the horizontal coordinates of the impact points of each water clot on the nozzle. Modeling was conducted in both two- and three-dimensional spaces, utilizing the k-ε model in an automated system specifically designed for plane shear layers and turbulent flows. This model includes the smallest set of equations to minimize unknown quantities in processes involving all natural heat and liquid flows. The study achieved favorable results when calculating shear stresses and Reynolds tensors for a medium with a small pressure gradient. The initial kinematic and dynamic parameters used in the model were determined based on formulas discussed in the previous chapter.

Handwritten signature preprocessing for off-line recognition systems

Akhundjanov,

Zulunov,

Kayumov

et al. 2024

In the process of handwritten signature recognition, preliminary processing of the signature is an important step before identifying informative features. The signatures of one person always have some differences, in addition, they can be different colors, different sizes and orientations. Once signatures are digitized, their images may contain some noise. The purpose of preliminary processing of a signature image is to obtain the most invariant representation of a digital image of a person’s signature, which will allow him to be identified or to establish that the signature is forged.