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In many applications, very fast methods are required for estimating of parameters of harmonic signals distorted by noise. Most of the known digital algorithms are not fully parallel, so that the speed of processing is quite limited. In this paper new parallel algorithms are proposed, which can be implemented by analogue adaptive circuits employing some neural networks principles. Algorithms based on the least‐squares (LS) and the total least‐squares (TLS) criteria are developed and compared. The problems are formulated as optimization problems and solved by using the steepest descent continuous‐time optimization algorithm. The corresponding architectures of analogue neuron‐like adaptive processors are also shown. The developed networks are more robust against noise in the measured signal than other known neural network algorithms. The network based on the TLS criterion optimizes the estimation under the assumption that the signal model can also be perturbated (frequency or sampling interval fluctuation and so forth). The TLS estimates are better and more reliable than the corresponding LS estimates, when applying a higher sampling frequency and a wider sampling window. The TLS algorithm is a generalization of the well known LMS rule and could be in some applications superior to the family of LMS algorithms. Extensive computer simulations confirm the validity and performance of the proposed algorithms.

The purpose of this paper is to compare the accuracy of tracking the amplitude and frequency changes of non‐stationary electric signals.

Short‐time fourier transform (STFT) and S‐transform algorithms were applied to analyze non‐stationary signals originating from switching of capacitor banks in a power system.

The S‐transform showed possibilities of sharp localization of the basic component, and allowed improvement of tracking dynamism the transient components in comparison to STFT.

S‐transform is a better tool for the analysis of non‐stationary waveforms in power systems and its properties can be used for diagnostic and power quality applications.

The dynamic tracking of the changes in time and frequency of real‐like signals originating from a power system are investigated in this paper.

This study aims to draw attention to consumers' behaviours which are changing on account of the COVID-19 pandemic, provide an understanding of the factors influencing these behaviours and emphasise their importance in building contemporary business models for the restaurant industry. The article is a case study of the Polish restaurant sector based on a comparison with the worldwide literature.

A study of the current literature on the subject pertaining to the issues discussed, an analysis of them, mainly by examining trade reports, with a special focus on the following databases (BDL GUS, CBOS, IGGP PKD) and foreign references, as well as Internet sources, using the systematic (structured) literature review (SLR) method. The authors searched the databases between May 2020 and May 2022, paying attention to the following keywords: COVID-19, consumer behaviours, food services, market segmentation, Poland.

The analysis allowed the authors to identify the most important factors influencing consumer behaviour under the influence of the COVID-19 pandemic. This in turn enabled them to verify a hypothesis concerning the significant impact of the COVID-19 pandemic on consumers’ behaviours on the food service market. Results from an analysis of trade reports and from a literature review confirm the hypothesis proposed, leading to the conclusion that the contemporary reality in Poland currently requires businesses to continuously monitor consumers’ behaviours in a turbulent and uncertain environment.

The systematic identification of changes taking place in consumers’ behaviours will make it possible to adapt a portfolio of services to changes observed in this regard.

The analysis conducted by the authors in 2021 to examine trends in consumer behaviours proved that changes affecting their thinking were undoubtedly accelerated by the pandemic of a contagious disease – COVID-19.

Some consumer trends that appear to be a response to limits and restrictions may be observed for a longer period of time. Therefore, those restaurant owners who want to successfully go through the stage of adaptation to the new reality will have to focus, in the short term, on actions designed to identify their customers’ needs and expectations anew and tailor their business models and offer accordingly.