# mathematical modeling

## Decrease of low-frequency spectral power in a heart rate variability signal in a mathematical model of the cardiovascular system of arterial hypertension patients

* Background and Objectives:* Index equal to the spectral power of the low-frequency oscillations from the time series of the time intervals between the hearts contractions are often used when investigating the cardiovascular system. Experimental studies have shown that this spectral index was a preclinical marker of cardiovascular diseases, including arterial hypertension and diabetes.

## Integrated research of the phase-shifting properties of a step structure of class II on connected transmission lines with mismatched loads

* Background and Objectives:* Fixed phase shifters on the transmission line are passive devices that provide a constant phase shift between the signals to the outputs of the reference and phase-shifting channels. They are the basic elements of electronic equipment for various functional purposes. One of the main tasks of frequency technology is to expand the working range of fixed phase shifters.

## Mathematical Modelling Multilayered Waveguides Magnitodielektrical Structures with Strip and Slot Elements on Borders of Section of Environments

The effective algorithm of modeling of difficult multilayered electrodynamics systems with strip and slot elements on borders of layers is presented. The approach to construction of algorithm of the automated designing of such systems by a given topology and parameters was developed.

## Mathematical Model of Vascular Tone Autoregulation

Background and Objectives: The conventional approach to study the blood circulat ion in the cardiovascular system of humans and animals is based on representation of the vascular system as a hierarchical structure of branching elastic tubes. While considerable progress has been achieved in the framework of this p aradigm, the other fails when one needs to analyze the dynamical patterns in networks of small arterial vessels.