Przeglądaj {{ collection }} wg Autor "Vik, Michal"

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Fabrication of UV-responsive chromic system using nanospider device and its photo-fatigue behavior under continuous mode of UV irradiance
(Wydawnictwo Politechniki Łódzkiej, 2022) Solanki, Utkarshsinh; Vikova, Martina; Holec, Pavel; Erben, Jakub; Vik, Michal
In this paper, we proposed the preparation of a photochromic nonwoven fabric based on photochromic nanofibers with high color response, which has excellent photochromic properties, good durability, and can quickly return to its original state. Photochromic nanofibers were colored by spiropyran (SP) class of photochromic dyes. The SP was dissolved in an ethanol solution containing polyvinyl butyral and then the composition was spined using a needle-free NANOSPIDER system. The test data of colorimetric and spectral characteristics of photochromic color change demonstrate that the prepared samples exhibit significant color changes and sufficient stability during fatigue tests. At the same time, a good agreement of the measured experimental data with the proposed theoretical model is documented, which allows estimating the total amount of energy that causes a 50% decrease in color response. This enabled the design of an accelerated UV resistance test method for photochromic textiles.
A review of lcam datasets and sève whiteness proposal
(Wydawnictwo Politechniki Łódzkiej, 2022) Mukthy, Azmary Akter; Vik, Michal; Viková, Martina
In our recent work, we investigated the validity of the newly proposed whiteness formula by Robert Sève [1] for our LCAM whiteness datasets under a LED light source of correlated color temperature (CCT) 5000K combined with Wood's UV-A lamp.We compared the CIE whiteness formula, the Ganz whiteness formula, and the Séve proposal to the results of visual assessment of forty white samples assessed by ten observers with normal color vision under experimental light source. Because the Sève proposal was derived from the CIE formula for whiteness considering whitespace, we were interested to see its impact on our datasets under test lighting different from D65.We have found that the Sève whiteness formula can predict maximum whiteness as a function of saturation for light conditions other than CIE D65, but visual observations of whiteness lead to an assessment of a significant drop in whiteness for materials with saturation between - 40 and -70 and luminance factor between 70 and 90. As expected, both the CIE whiteness formula and the Ganz formula correlated strongly with visual observations. In the case of the CIE equation, a high correlation coefficient of 0.84 was measured compared to the newly proposed W2,n equation where a value of 0.71 was found. In other words, with a very intense UV source, the intensity of which is above the UV fraction of the corresponding CIE illuminations D, the colouration of the samples containing FWA is highly saturated. This fact is not taken into account in the case of the CIE equation. Dr. Sève's new proposal addresses this problem, but sufficient new visual experiments need to be set up so that the parameters of this equation can be optimised.