In this note, a formula for the lower Bohl exponent of a discrete system with variable coefficients and weak variation was proved. This formula expresses the Bohl exponent through the eigenvalues of the coefficient matrix. Based on these formulas a necessary and sufficient condition for an uniform exponential instability of such systems is also presented.

In this study, a procedure for optimal selection of measurement points using the D-optimality criterion to find the best calibration curves of measurement sensors is proposed. The coefficients of calibration curve are evaluated by applying the classical Least Squares Method (LSM). As an example, the problem of optimal selection for standard pressure setters when calibrating a differential pressure sensor is solved. The values obtained from the D-optimum measurement points for calibration of the differential pressure sensor are compared with those from actual experiments. Comparison of the calibration errors corresponding to the D-optimal, A-optimal and Equidistant calibration curves is done.

The paper presents application of a modified, symmetrical Bouc-Wen model to simulate the mechanical behaviour of high-frequency piezoelectric actuators (PAs). In order to identify parameters of the model, a two-step algorithm was developed. In its first stage, the mechanical parameters were identified by taking into account their bilinear variability and using a square input voltage waveform. In the second step, the hysteresis parameters were determined based on a periodic excitation. Additionally, in order to reduce the influence of measurement errors in determination of selected derivatives the continuum wavelet transform (CWT) and translation-rotation transformation (TRT) methods were applied. The results proved that the modified symmetrical Bouc-Wen model is able to describe the mechanical behaviour of PAs across a wide frequency range.

The general view of Tadeusz Rittner, a highly successful playwright of the early 20th century, as an uncommitted realist and author of ‘well-made plays’ has, no doubt, been formed and fixed by Zbigniew Raszewski, renowned historian of the theatre who wrote the introductions to the postwar editions of Rittner's plays. This article shows a rather different picture of Rittner, based on his journalism, autobiographical novels and lesser-known dramas in which he pursued his innovatory theatrical visions. The complete Rittner is, in fact, made up of metatheatricality, the grotesque, the aes-thetics of Viennese modernism and a fair share of commercialism.

Climate change has been affecting plants over the last century and caused

changes in life history features such as the flowering time. Herbarium specimens provide

a snapshot of the past environmental conditions during their collection. The collection

date in a herbarium specimen is a good proxy to determine the flowering period (phenology).

In this study, phenological data from subarctic plant specimens collected over

100 years were gathered by using one of the largest herbarium databases in the World.

The collection dates of 7146 herbarium specimens were analyzed and significant shifts

in the phenology of subarctic plants were detected. In this study, most of the analyzed

142 species in a subarctic biogeographic region tended to flower earlier in the 1950–2018

period compared to the 1900–1949 as a possible result of the climate change. Flowering

time shifted from 8 to 26 days in some species. Changes in flowering time may

alter species interactions, community composition, and species distribution in a region.

Therefore, results of this study may shed light on the possible shifts in phenology and

plant responses under the climate change.