GEOMETRIC MODELING OF A SHAPE OF PARALLELOGRAM PLATES IN A PROBLEM OF FREE VIBRATIONS USING CONFORMAL RADII

The paper considers a method of geometric modeling applied when solving basic twodimensional problems of the theory of elasticity and structural mechanics, in particular the applied problems of engineering. The subject of this study is vibrations of thin elastic parallelogram plates of constant thickness. To determine a basic frequency of vibrations, the interpolation method based on the geometric characteristic of the shape of plates (membrane, cross sections of a rod) is proposed. This characteristic represents a ratio of interior and exterior conformal radii of the plate. As is known from the theory of conformal mappings, conformal radii are those obtained by mapping of a plate onto the interior and exterior of a unit disk. The paper presents basic terms, tables, and formulas related to the considered geometric method with a comparative analysis of the curve diagrams obtained using various interpolation formulas. The original computer program is also developed. The main advantage of the proposed method of determining the basic frequency of plate vibrations is a graphic representation of results that allows one to accurately determine the required solution on the graph among the other solutions corresponding to the considered case of parallelogram plates. Although there are many known approximate approaches, which are used to solve the considered problems, only geometric modeling technique based on the conformal radii ratio gives such an opportunity.

ACOUSTIC CHARACTERISTICS OF DIPHTHONGS AND TRIPHTHONGS IN MODERN GERMAN

Acoustic characteristics of diphthongs and triphthongs in modern German. The article covers the issues of phonetic-phonological status of diphthongs in modern vocalism of the German language. To answer this question, an instrumental study of the acoustic characteristics was performed: intensity (I), basic frequency (F), duration (t) of diphthongs and their constituent components compared to short and long monophthongs in the same consonant environment. The combination of diphthongs followed by vowels, which are inherent in modern German and are interpreted in the article as triphthongs, since they have their own phonetic characteristics, are also considered.

K Intonologickej Charakteristike Slabiky V Slovenčine

The paper analyses the intonation of syllables in broadcasted communication utterances (analyzing audio samples from radio programs Rádiožurnál and Literárna revue Rádia Slovensko) from theoretical point of view, while building upon the outcomes of the experimental phonetic research. Duration of the individual segments, intensity of sonantic cores including intensity of syllables and basic frequency F0 were analysed. Role of the analysed parameters in relation to the sonic formation of the text can be seen in exact graphs, which are cross-referenced by the measured values. The analysis has shown that an intonation differentiation of text-forming features in the broadcasted communication utterances is significantly influenced by tonal modulation (melody). Variation potential of time modulation is limited by faster pace of broadcasted texts. The strength modulation is demonstrably limited by signal standardization in radio broadcasting.

Mobile Device for Monitoring of Cardiovascular System State Based on Assessment of Synchronization of its Low-Frequency Rhythms

We develop an autonomous mobile device for continuous monitoring of cardiovascular system functional state, which is based on the assessment of synchronization between the low-frequency oscillations in heart rate and blood flow having a basic frequency close to 0.1 Hz.

Time Varying Hydrodynamics Identification of a Flexible Riser Under Multi-Frequency Vortex-Induced Vibrations

In this paper, Forgetting Factor Recursive Least Squares (FF-LS) method is proposed to identify time-varying vortex-induced force coefficients of the flexible riser under multi-frequency VIV. FF-LS method introduces the forgetting factor, which gives more weight to the data closer to the present. This modification improves the method’s sensitivity to the time-varying parameters, and enables it to identify the time-varying parameters under multi-frequency coupling. In this paper, the mass-spring-dashpot model is used to verify FF-LS method’s ability to accurately identify time-varying parameters under multi-frequency coupling. Then, this methodology is used to identify the vortex-induced force coefficients of flexible riser at the basic frequency when vortex-induced vibration occurs. Identified coefficients are consistent with the result obtained from Least Squares method, which indicates that the proposed FF-LS method retrogrades to the Least Squares method when VIV response and the vortex-induced force contains only one single frequency. Finally, this methodology is used to identify the time-varying vortex-induced force coefficients of a flexible riser under VIV considering the coupling effect between the basic frequency and high frequency. The vortex-induced force reconstructed from identified time-varying coefficients is consistent with real vortex-induced force, which verifies the validity and applicability of this methodology in identifying time-varying vortex-induced force coefficients considering multi-frequency coupling effect. The results show that when the flexible riser is subjected to multi-frequency VIV, its vortex-induced force coefficients change periodically, the time-averaged values of these time-varying coefficients are different from the vortex-induced force coefficients at the basic frequency, which results from the coupling effect between the basic frequency and high frequency. Linear superposition of vortex-induced force coefficient at basic frequency and high frequency are different from time-varying coefficients considering coupling effect of multi-frequency and cannot reconstruct vortex-induced force correctly.