Papers by Viktor Witkovsky
Journal of Neurophysiology
The interpretation of gamma activity in response to noxious and innocuous somatosensory stimuli h... more The interpretation of gamma activity in response to noxious and innocuous somatosensory stimuli has sparked controversy. Here, we show that participants’ gamma oscillations measured through electroencephalography vary. Although some participants do not show a distinct gamma response, others exhibit stable and reliable response patterns in terms of time, frequency, and magnitude.
Applications of Mathematics, 1992
Institute of Mathematics of the Czech Academy of Sciences provides access to digitized documents ... more Institute of Mathematics of the Czech Academy of Sciences provides access to digitized documents strictly for personal use. Each copy of any part of this document must contain these Terms of use.
Metrology
The Tsallis q-Gaussian distribution is a powerful generalization of the standard Gaussian distrib... more The Tsallis q-Gaussian distribution is a powerful generalization of the standard Gaussian distribution and is commonly used in various fields, including non-extensive statistical mechanics, financial markets and image processing. It belongs to the q-distribution family, which is characterized by a non-additive entropy. Due to their versatility and practicality, q-Gaussians are a natural choice for modeling input quantities in measurement models. This paper presents the characteristic function of a linear combination of independent q-Gaussian random variables and proposes a numerical method for its inversion. The proposed technique makes it possible to determine the exact probability distribution of the output quantity in linear measurement models, with the input quantities modeled as independent q-Gaussian random variables. It provides an alternative computational procedure to the Monte Carlo method for uncertainty analysis through the propagation of distributions.
2023 14th International Conference on Measurement
Series on Advances in Mathematics for Applied Sciences, 2018
Series on Advances in Mathematics for Applied Sciences, 2022
2017 11th International Conference on Measurement, 2017
One of the most substantial issues of evaluation a gauge calibration is to determine the calibrat... more One of the most substantial issues of evaluation a gauge calibration is to determine the calibration function. In pursued situation, it means to estimate the parameters of the linear function which express the dependence of the (errorless) measured values using the calibrated gauge on the true measured quantities. Of course, we are interested also in uncertainties of the estimated parameters. In contribution are shown two methods solving the problem. The first one is an approximative method using the linear model of indirect measurements. The second one is a proper approach using the linearized model of direct measurements with nonlinear conditions on the parameters.
Uvažuju sa a porovnavaju niektore metody na konstrukciu približných konfidencných intervalov v pr... more Uvažuju sa a porovnavaju niektore metody na konstrukciu približných konfidencných intervalov v pripade digitalizovaných merani.
We are developing a computer program to calculate tail probabilities of random variables from the... more We are developing a computer program to calculate tail probabilities of random variables from their characteristic functions. This code written in Matlab and is an implementation of method described in (1). We present some practical results. The need for such calculations appears naturally e.g. in metrology: in the problem of calibration (2) and/or in determination of the reference values in interlaboratory comparisons (3). Currently, as suggested by GUM and its Supplement 1 (4), such problems are typically solved by propagation of distributions using a Monte Carlo method.
Mathematica Slovaca, 2021
Analyzed is the comparative calibration problem in the case when linear relationship is assumed b... more Analyzed is the comparative calibration problem in the case when linear relationship is assumed between two considered measuring devices. The first method for obtaining the approximate confidence region for unknown parameters of the calibration line applies the maximum likelihood estimators of the unknown parameters. The second method is based on estimation of the calibration line via replicated errors-in-variables model. The two methods are compared.
2017 11th International Conference on Measurement, 2017
Quadrature homodyne interferometers are frequently used in dimensional metrology. Their measureme... more Quadrature homodyne interferometers are frequently used in dimensional metrology. Their measurement signals exhibit offsets, unequal amplitudes and phase difference. Frequently, there exists a significant component of the measurement noise common to both (Sine and Cosine) quadrature signals, such that the noise of quadrature signals is correlated. Presented is a method for estimation the unknown correlation coefficient from the measured data, provided that the Sine and Cosine signal noise follow particular autoregressive process (here we consider the AR(1) process). The estimate of the correlation coefficient and of the parameters of the noise autoregressive process are utilized in the iterative algorithm for demodulation and evaluation of the amplitude noise related uncertainty contribution of correlated quadrature interferometer signals, originally proposed by Koning, Wimmer and Witkovsky in [1] for uncorrelated interferometer signals.
Abstract. The measurement signals of the quadrature homodyne interfe rometers (say x and y, usual... more Abstract. The measurement signals of the quadrature homodyne interfe rometers (say x and y, usually called Sine/Cosine signals and/or quadrature sig nals) typically exhibit offsets, unequal amplitudes and a phase difference that is not exactly 90 degree as would be expected in the ideal/theoretical case. Moreover, frequently there is a ignificant component of the measurement noise which is common to both signals (caused, e.g., by the amplitude noise of the laser), and as such, it results in a non vanishing correlatio n of the measured signals. Here we present a method for estimation of the unknown correlation co efficient from the observed data and suggest its implementation into the algorithm for demod ulation and evaluation of the amplitude noise related uncertainty contribution of correla ted quadrature interferometer signals, originally proposed by Köning, Wimmer and Witkovský in [ 2] for uncorrelated interferometer signals.
We introduce a class of logarithmic Lambert W random variables for a specific family of distribut... more We introduce a class of logarithmic Lambert W random variables for a specific family of distributions. In particular, we characterize the log-Lambert W random variables for chi-squared distributions which naturally appear in the likelihood based inference of normal random variables.
Discussed is the problem of evaluation the measurement results from the simple Key Comparisons in... more Discussed is the problem of evaluation the measurement results from the simple Key Comparisons in metrology. Presented and described is a new method for evaluation the Key Comparison Reference Value and its expanded uncertainty based on metrological approach, together with the basic statistical (frequentist) properties.
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Papers by Viktor Witkovsky