An experimental investigation of viscosity of a newly developed natural polymer-based media for abrasive flow machining (AFM) of 3D printed ABS parts

Abrasive Flow Machining (AFM) is the method of finishing complex surfaces and internal channels with the help of extrusion pressure and abrasive-laden viscoelastic polymer media. This paper is based on developing a new AFM media using a natural waste polymer as a base material. In the article, a natural polymer media viz. rice husk ash-based media has been developed, and subsequently, rheological analysis has been done, and experimentation has been performed on Anton-paar® rheometer to optimize the viscosity of these newly developed AFM media. In this research study, the hollow elliptical shape of ABS (acrylonitrile-butadiene-styrene) material was manufactured using the FDM technique and then finished with a one-way AFM machine. This paper examined the parametric dependencies of AFM process parameters on finishing FDM printed hollow elliptical parts. The improved surface roughness of the FDM printed hollow elliptical parts has been investigated relating to the AFM process parameters. The maximum surface roughness has been achieved by 95.98%.

Numerical study of a model of terahertz collective modes in DNA

Terahertz density fluctuations in DNA have been recognized to be associated with biological function of DNA and widely studied both experimentally and theoretically. In the present work, we investigate numerically a new model for the terahertz dynamics of density fluctuations in DNA, proposed earlier. This model considers the length scales corresponding to wave numbers up to the position of the maximum of the static structure factor and allows to reflect structural effects caused by the dependence of the static structure factor on wave number. We study the parametric dependencies of the model to elucidate the effect of dlocalization of the dynamics of density fluctuations caused by structural effects.

Dynamics of tax revenues in the budget of Ukraine and their forecast during the crisis period

It is extremely important for the budget process to obtain accurate forecasts of potential tax revenues, especially in periods of disruption and crisis. The paper is devoted to the study of dynamics of tax revenues’ volumes in the budget of Ukraine and the forecast of their values during the crisis.The dynamics of tax revenues in the Consolidated Budget of Ukraine, studied by using randomized R|S-analysis, fractal and probabilistic analyses as well as entropy calculation based on the data on monthly tax revenues for the period 2011–2021, is anti-persistent, fractal-like and unpredictable based on parametric dependencies, simple and complex trends. The topological dimension of the lines of dynamics for tax revenues of all types of taxes is much higher than 1, and the Hirst index indicates either fractal similarity of dynamics or its chaos. The map of dissipation periods of tax revenues in Ukraine, determined on the basis of entropy calculation and periods of negative entropy production according to the dynamics of tax revenues, coincided with the periods of maximum reduction in their volumes. The most crisis periods in the formation of tax revenues are 2019–2020, for certain types of taxes – 2016–2020, but the dissipation of tax revenues is projected for 2021–2022.The comparison of the level of fractal similarity in dynamics of the volume of tax revenues and peculiarities of the dynamics of entropy and entropy production, allowed to substantiate the division of taxes into nine types, of which five were found in Ukraine.