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2 results on '"Curvature"'

1. Applications of the Frenet Frame to Electric Circuits.

Author

Milano, Federico, Tzounas, Georgios, Dassios, Ioannis, and Kerci, Taulant

Subjects
*TORSION, *ELECTRIC circuits, *CURVATURE, *PHASOR measurement, *TIME-frequency analysis, *DIFFERENTIAL geometry, *VOLTAGE
Abstract

The paper discusses the relationships between electrical quantities, such as voltages, currents, and frequency, and geometrical ones, namely curvature and torsion. The proposed approach is based on the Frenet frame utilized in differential geometry and provides a general framework for the definition of the time derivative of electrical quantities in stationary as well as transient conditions. As a byproduct, the proposed approach unifies and generalizes the time- and phasor-domain frameworks. Other noteworthy results are a new interpretation of the link between frequency and the time derivatives of voltage and current; and a definition of the rate of change of frequency that includes the novel concept of “torsional frequency.” Several numerical examples based on balanced, unbalanced, harmonically-distorted and transient voltages illustrate the findings of the paper. [ABSTRACT FROM AUTHOR]

Published
2022
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2. Results of testing the comparatory method: The curvature of the shell valve frontal section is inappropriate as a systematic character for the freshwater pearl mussel of the genus Margaritifera.

Author

Bolotov, I., Makhrov, A., Bespalaya, Yu., Vikhrev, I., Aksenova, O., Aspholm, P., Gofarov, M., Ostrovskii, A., Popov, I., Pal'tser, I., Rudzite, M., Rudzitis, M., Voroshilova, I., and Sokolova, S.

Subjects
*MARGARITIFERA, *CURVATURE, *FRESHWATER mussels, *PEARL oyster culture, *BIOLOGICAL variation
Abstract

This paper continues a discussion on the number of pearl mussel species of the genus Margaritifera in northern Europe. A biometric study of 1711 pearl mussel Margaritifera margaritifera shells from 15 rivers in Russia and Latvia (basins of the White and Baltic seas) has been conducted. All the examined samples fall into two groups: the northern group (with the shells more flattened on average, f. margaritifera) and the southern one (with more convex shells, f. elongata); the boundary between these groups is at 63° N. Analysis of intrapopulation variation has shown that the samples contain individuals that correspond to f. margaritifera, f. elongata, and f. borealis. However, any hiatus between these forms is absent in all the samples, and individuals belonging to two intermediate forms are rather frequent. The hypothesis on the species specificity of the shell valve frontal section has not been confirmed based on examination of large shell samples. The pearl mussels inhabiting rivers of Northern Europe belong to a single species, M. margaritifera. [ABSTRACT FROM AUTHOR]

Published
2013
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