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Recent Submissions

Flow over thin-plate weirs with a triangular notch – influence of the relative width of approach channel with a rectangular cross-section
(Institute of Hydrology of the Slovak Academy of Sciences, 2024-06-01) Pospíšilík, Šimon; Zachoval, Zbyněk; Gabriel, Pavel
The article deals with the determination of the influence of the relative width of an approach channel with a rectangular cross-section on the discharge of clean water flowing over thin-plated weirs with a triangular notch and zero height of the weir above the bottom of the approach channel. To evaluate the influence, the Kindsvater-Shen equation was modified by introducing the basic effective discharge coefficient and the coefficient of the relative width of the approach channel. The coefficient of the relative width of the approach channel was determined based on the evaluation of data from three extensive experimental research investigations. It is valid for the entire possible range of relative widths of the approach channel and for the range of notch angles from 5.25° to 91.17°. The relative error of discharge determination is approximately up to ±2% over the entire range of discharges used in the conducted experimental research. The evaluation made it possible to determine the boundary distinguishing the partially contracted weirs from the fully contracted weirs in terms of impact on discharge.
Novel voltage Multiplier/Divider-based active square law detector for heartbeat measurement
(ELSEVIER SCI LTD, 2024-02-28) Šotner, Roman; Polák, Ladislav; Jeřábek, Jan; Langhammer, Lukáš; Freeborn, Todd
This paper describes a novel active voltage detector that is capable of processing analog signals with levels from units of mV up to 250 mV. An advantage of the proposed circuit is that the relationship between output voltage and input level is not linear but quadratic, which increases the sensitivity when processing low-level signals. The presented solution has tuning parameters for correction or intentional shift of internal DC offset and electronic control of the output signal gain level. The application example presents detection of beats per minute (BPM) in the range of 6-300 BPM, which corresponds to a frequency range of 0.1-5 Hz. The advantage of the presented solution is that the output of the circuit is directly a digital signal compatible with TTL levels, so there is no need for any analog to digital converter to produce a digital signal for further processing.
Free-Standing Bacterial Cellulose/Polypyrrole Composites for Eco-Friendly Remediation of Hexavalent Chromium Ions
(American Chemical Society, 2024-05-16) Stříž, Radim; Minisy, Islam; Bober, Patrycja; Taboubi, Oumayma; Smilek, Jiří; Kovalčík, Adriána
Drinking water quality requirements are getting stricter but water sources are limited. Therefore, effective ways to purify it must be developed. In order to remove toxic Cr(VI) from wastewater, efficient, nontoxic, sustainable, resilient biocomposites based on bacterial cellulose (BC) and polypyrrole (PPy) have been fabricated. The free-standing BC/PPy composites, allowing easy handling during and after water treatment, were successfully prepared by the oxidative polymerization of pyrrole on the BC surface. The variation in the physical state of BC sheets used for coating by PPy was done to study the rheological properties and Cr(VI) removal capacity. Characterization techniques like FTIR, SEM, BET, thermogravimetric analysis, and rheological analyses established the morphology and structural properties of the prepared biocomposites. The physical state of the bacterial cellulose used for the coating by PPy positively affected the mechanical and thermal stabilities of the resulting BC/PPy composites but had almost no effect on the removal capacity of hexavalent chromium. The free-standing BC/PPy composites reached a specific surface area of 61.96 m2 g–1 and a pore volume of 0.097 cm3 g–1, showing more than a threefold increase compared to neat BC sheets. The coating of BC by PPy markedly improved the maximum adsorption capacity of Cr(VI). The experimental Cr(VI) adsorption data fitted using Langmuir’s isotherm model indicated homogeneous monolayer adsorption of Cr(VI) ions onto the BC/PPy surface. The Cr(VI) maximum adsorption capacity of BC/PPy composites was determined to be 294.1 mg g–1. Furthermore, the BC/PPy composites were proved to be excellent catalysts for the photocatalytic reduction of toxic Cr(VI) into nontoxic Cr(III) ions. These results suggest that the free-standing BC/PPy composites could be used as alternative materials for eco-friendly remediation of hexavalent chromium ions from wastewater.
Methylmercury Effect and Distribution in Two Extremophile Microalgae Strains Dunaliella salina and Coccomyxa onubensis from Andalusia (Spain)
(MDPI, 2024-02-21) Šimanský, Samuel; Holub, Jiří; Márová, Ivana; Cuaresma, María; Garbayo Nores, Ines; Torronteras, Rafael; Vílchez, Carlos; Gojkovic, Živan
The main entrance point of highly toxic organic Hg forms, including methylmercury (MeHg), into the aquatic food web is phytoplankton, which is greatly represented by various natural microalgal species. Processes associated with MeHg fate in microalgae cells such as uptake, effects on cells and toxicity, Hg biotransformation, and intracellular stability are detrimental to the process of further biomagnification and, as a consequence, have great importance for human health. The study of MeHg uptake and distribution in cultures of marine halophile Dunaliella salina and freshwater acidophilic alga Coccomyxa onubensis demonstrated that most of the MeHg is imported inside the cell, while cell surface adhesion is insignificant. Almost all MeHg is removed from the culture medium after 72 h. Significant processes in rapid MeHg removal from liquid medium are its abiotic photodegradation and volatilization associated with algal enzymatic activity. The maximum intracellular accumulation for both species was in 80 nM MeHg-exposed cultures after 24 h of exposure for D. salina (from 27 to 34 mu g/gDW) and at 48 h for C. onubensis (up to 138 mu g/gDW). The different Hg intakes in these two strains could be explained by the lack of a rigid cell wall in D. salina and the higher chemical ability of MeHg to pass through complex cell wall structures in C. onubensis. Electron microscopy studies on the ultrastructure of both strains demonstrated obvious microvacuolization in the form of many very small vacuoles and partial cell membrane disruption in 80 nM MeHg-exposed cultures. Results further showed that Coccomyxa onubensis is a good candidate for MeHg-contaminated water reclamation due to its great robustness at nanomolar concentrations of MeHg coupled with its very high intake and almost complete Hg removal from liquid medium at the MeHg levels tested.
AI: All Idiots
(Masaryk University Press, TIC Brno, 2022-12-01) Trnková, Barbora
This article creates a cross section across artistic and artificial intelligence, providing the conceptual basis and examples of the implementation of the group exhibition project AI: All Idiots, which was part of the Other Knowledge exhibition series at the MeetFactory Gallery in Prague in 2021. The purpose of the project was to bring the subject of modern artificial intelligence to the attention of the general public while still being artistically stimulating. In lieu of the conventional strategy of curating a selection of artworks created by artists working with AI, we opted to start from scratch by gathering online digital copies of selected artworks by Czech artists, which served as a training dataset for our original AI software. The artists were also involved in the data’s interpretation. The experiment addressed the widespread use of AI for web content analysis, artists, curators, and the art community as a whole, as well as the question of whether AI operates as a source of information to generate stereotypical products that cannot do more than statistically confirm and continously repeat what is already known. The article sheds some light on the question of how art engages in a creative dialogue with a world co-created by digital technologies and learning algorithms with their own agendas, without falling prey to a mechanical confirmation of stereotypes. The source of artificial intelligence’s creativity draws from tuning expected and unexpected patterns and schemas. Like a sensitive photographic material, the architecture of art’s hidden structures is gradually revealed, intensifying the characteristics of the prejudices and habits we connect with art. If art is defined as revealing the invisible, then artificial intelligence is a useful artistic instrument.