Izvestiya of Saratov University.
Physics
ISSN 1817-3020 (Print)
ISSN 2542-193X (Online)

spectral analysis

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.

Nanodisplacement measurements by frequency-modulated laser autodyne

Background and Objectives: Measurements of nanodisplacements are relevant for various applications of self-mixing laser (autodyne), in particular when they are combined with microwave probe methods, which are sensitive not only to the profile, but also to the inhomogeneities of the material and the its internal structure. A laser autodyne method for measuring the nanodisplacement by triangular frequency modulation of the laser radiation is proposed.

Distance Measurement with Harmonic Modulation of Self-Mixing Laser Wavelength at External Optical Feedback

Background and Objectives: Self-mixing interferometry of absolute distances is currently well represented by the method of frequency modulation of the laser diode supply current (FMCW). In recent years a harmonic modulation of the power current of a self-mixing laser began to be used. The advantage of the harmonic modulation method is due to the absence of the need to adjust the deviation of the radiation wavelength when changing the distance to the reflector.