Technical University of Liberec
Recent publications
Environmental pollution is among the biggest challenges faced by the global society today. This is largely due to rapid urbanization and industrialization. As a result, more and more research focuses on alternative methods of remediating and preserving contaminated ecosystems. Among such techniques, nanomaterials have become an exciting and evolving area of study. One such nanomaterial that has been shown to play a key role in environmental remediation is metal oxide nanoparticles. Due to their unusual physicochemical properties, such as abundant surface‐active sites, tailorable size and shape, and high chemical stability, metal oxide nanoparticles have continued to draw considerable attention. Several metal oxide nanoparticles have been synthesized over the last several decades via physical, chemical, and biological means and their uses have been studied in numerous environmental remediation techniques. Despite being used in various roles, metal oxide nanoparticles are commonly used as adsorbents, catalysts, or antimicrobial agents. This chapter briefly presents the various techniques of metal oxide nanoparticle synthesis, their mechanism of remediation with brief overview of most commonly used metal oxide nanoparticles, such as TiO 2 , ZnO, iron oxides, CuO, SnO 2 , and WO 3 .
Many aspects of sulfate radical-advanced oxidation processes, particularly under alkaline medium, are largely debatable. Based on the available literature, the possible mechanisms of both activation of peroxydisulfate (PDS) and peroxymonosulfate (PMS) under alkaline conditions are reviewed. Thereby, several products (SO5²⁻, HO2⁻) are formed presenting a complex interplay since they may be involved in persulfate activation and radical scavenging. Since both PMS and HO2⁻ have dissociation centers, alkaline activation of persulfates is very strongly dependent on pH. Owing to some inconsistencies in the state-of-the-art literature, it seems that the activation of both PDS and PMS should be reconsidered in more detailed mechanistic studies. Relevant for alkaline activation, sulfate radical-based oxidation of hydroxide ions yielding hydroxyl radicals is not important for pH< 10.4 in chloride-poor waters (<<1.0 mM), while in the presence of chloride (e.g. 1.0 mM), hydroxyl radicals may be the most important reactive species.
In the linear regression model with possibly autoregressive errors, we construct a family of nonparametric tests for significance of regression, under a nuisance autoregression of model errors. The tests avoid an estimation of nuisance parameters, in contrast to the tests proposed in the literature. A simulation study illustrate their good performance.
The cyclic oxidation behaviour of Fe-26Al-3Nb, Fe-27Al-5Nb and Fe-26Al-5Nb-1.4C (in at%) was investigated at 900°C. Chemical and phase analyses of the scale and oxide protrusions were conducted using light optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The oxidation resistance of the tested alloys was determined using fractal dimension, and the results were compared with Fe-26Al-0.3Zr, Fe-26Al-1Zr (at%) and EN X5CrNi18-10 steel. The oxidation kinetics of Fe-26Al-3Nb and Fe-27Al-5Nb follow the parabolic rate law. Oxidation ingress into the alloys was observed due to the preferential oxidation of niobium-rich precipitates. Therefore, the oxidation rate of tested alloys increased with increasing amounts of particles of Laves phase (Fe, Al)2Nb and NbC. The niobium carbides oxidised more readily than the particles of Laves phase (Fe, Al)2Nb. The cyclic oxidation of Fe-Al-Nb and Fe-Al-Nb-C alloys at 900°C led to the formation of oxide scales composed of Al2O3, Fe2O3 and AlNbO4 (or non-stoichiometric AlNbO4). Graphical Abstract
Flexible strain sensors have attracted numerous attentions due to their application in wearable devices. However, it is still a significant challenge to fabricate flexible strain sensors with both wide sensing range and high sensitivity simultaneously. In this article, this challenge had been addressed by using ultralong silver nanowires (AgNWs) to composite with stretchable thermoplastic polyurethane (TPU). Benefitted by the ultralong AgNWs, stretchable TPU and the hydrogen bond interaction between TPU and PVP on the surface of the ultralong AgNWs, the AgNWs/TPU composite flexible strain sensor with wide sensing range and high sensitivity simultaneously was achieved. The obtained AgNWs/TPU composite flexible strain sensor possessed wide sensing range above 250% with high gauge factor (GF) of 329.43 and excellent stability. The sensing range and GF of the obtained AgNWs/TPU composite flexible strain sensor were higher than those of other similar flexible strain sensor reported in the literature. The response and recovery times were about 100 and 300 ms, respectively. The AgNWs/TPU composite flexible strain sensor could be used to detect human motions such as finger, wrist, elbow, and knee bending as well as facial expressions and micro-acoustic vibrations. The AgNWs/TPU composite flexible strain sensor demonstrates excellent potential for applications in wearable device.
Halogenated organic compounds are naturally occurring in subsurface environments; however, accumulation of the degradative intermediate cis-1,2-dichloroethene (cDCE) at soil and groundwater sites contaminated with xenobiotic chlorinated ethenes is a global environmental and public health issue. Identifying microorganisms capable of cDCE degradation in these environments is of interest because of their potential application to bioremediation techniques. In this study, we sequenced, assembled, and analyzed the complete genome of Acinetobacter pittii CEP14, a strain isolated from chloroethene-contaminated groundwater, that has demonstrated the ability for aerobic cometabolic degradation of cDCE in the presence of n-hexane, phenol, and toluene. The A. pittii CEP14 genome consists of a 3.93 Mbp-long chromosome (GenBank accession no. CP084921) with a GC content of 38.9% and three plasmids (GenBank accession no. CP084922, CP084923, and CP084924). Gene function was assigned to 83.4% of the 3,930 coding DNA sequences. Functional annotation of the genome revealed that the CEP14 strain possessed all genetic elements to mediate the degradation of a range of aliphatic and aromatic compounds, including n-hexane and phenol. In addition, it harbors gene clusters involved in cytosol detoxification and oxidative stress resistance, which could play a role in the mitigation of toxic chemical intermediates that can arise during the degradation of cDCE. Gene clusters for heavy metal and antibiotic resistance were also identified in the genome of CEP14. These results suggest that CEP14 may be a versatile degrader of xenobiotic compounds and well-adapted to polluted environments, where a combination of heavy metal and organic compound pollution is often found.
The need to evaluate suppliers from the perspective of risk analysis by purchasing companies is increasing. Such evaluation of suppliers is conducted primarily by production companies with implemented quality (QMS), environmental (EMS), health and safety management systems (H&SMS), as well as Toyota Production System (TPS). This article aims to examine latent factors for suppliers' evaluation and to describe the intensity of these factors by the implemented management system. The article provides the results of empirical research conducted with the computer-assisted telephone interviewing (CATI) technique in 151 medium and large manufacturing companies operating in Poland. The risk was classified into three main groups to deepen the research process: management system risks, environment risks, and process risks. This allowed for the formulation of some original conclusions. The results showed that companies implementing standardized management systems take the issue of risk analysis and management more seriously than organizations that do not implement such systems. The research also highlighted the differences in the perception of risk caused by implementing various management systems. The study also found that the industry and business profile specificity also affect the risk assessment in cooperation with suppliers.
Over the past decade, there have been many successful attempts at artificially reproducing the surface structures found on natural superhydrophobic surfaces. The researchers have been working to mimic the nature by inducing superhydrophobic properties into a variety of material surfaces so that they exhibit non-wetting and self-cleaning properties. The superhydrophobic surfaces exhibits the water contact angles greater than 150° and roll-off angle less than 10°. Many diverse applications have been found in the fields, such as space, textiles, marine, defense, automotive, biomedical applications and engineering, sensors, apparels, and so on. This review paper is about the theories, fundamentals and recent developments in the field of superhydrophobic surfaces and their potential applications.
Advanced solid phase extraction (SPE) fibrous sorbents including polyethylene, polypropylene poly (hydroxybutyrate), and polyamide 6 nanofibers, polycaprolactone microfibers/nanofibers, polycaprolactone microfibers/polyvinylidene difluoride nanofibers, and poly (hydroxybutyrate) microfibers/polypropylene microfibers composites, as well as commercial molecularly imprinted polymers and restricted access media sorbent were compared in terms of bisphenols extraction from milk and their clean-up efficiency. Three on-line SPE-HPLC methods were completely validated for the extraction and detection of bisphenols A, AF, C, A diglycidyl ether, and F diglycidyl ether in bovine milk. Polycaprolactone composite nanofibers compared favorably to restricted access media, enabled excellent clean-up of bisphenols from the proteinaceous matrix, and yielded recoveries 98.0–124.5% and 93.0–115.0%, respectively, with RSD less than 10%. Total analysis time including on-line SPE step lasted only 12 min, which represents a significant reduction in time compared with previously reported as well as official European Union and AOAC methods defined for the determination of bisphenols in various matrices.
Rice husks are among the world's most significant agricultural waste. On the one hand, their use is related to solving an environmental problem; on the other hand, they use this material as a potential advanced material for many applications. Due to their chemical composition, rice husks can be a source of cellulose fibers and silica nanoparticles. The present text presents the essential characteristics of fibers and nanoparticles that were obtained from the treated shells at the same time. The fibers released from the rice husks have diameters ranging from 5 to 10 μm, the length being in the hundreds of micrometers. The surface of the fibers is not smooth, a sub-micrometer structure is visible, which indicates the potential possibility of further pulping into nanofiber formations. Silica nanoparticles are found on the surface of fibers released from rice husks and beyond. Nanoparticles form clusters of tens of nanometers; the sizes of individual particles are at the level of nanometer units. In the modified hulls, the accompanying technique did not identify the accompanying elements found in the original rice hulls.
The paper introduces the concept of the rational design of a deployable humeral intramedullary nail plug based on a honeycomb structure used for the surgical treatment of humeral shaft fractures. The concept serves for to restore the axial alignment of bone fragments and to maintain stability via bone-nail friction and locking screws. The design nail plug was gained by optimisation process the Latin Hypercube Sampling Design algorithm and Multi-Objective Genetic Algorithm. It was shown that we can use statistical shape function combined by 3 D printing for designing of a new rationally designed implants.
In this paper, microstructural and tribological properties of valve seats made of ADI and Q – cryo cast iron with spheroidal graphite have been investigated in comparison to stellite 6. The studies have shown that the cheaper variant of cast iron thermally threated can have comparable properties suitable for valve seats usage in gas combustion engines. In the work the tribological test was performed and resulted into the course of friction coefficient of the tested samples and selected properties as the thickens of the valve seat or hardness and Young modulus after cast iron thermal treatment were measured.
Background This study examined the strength, shape and direction of associations of accelerometer-assessed overall, school- and non-school-based moderate-to-vigorous physical activity (MVPA) and sedentary time (ST) with BMI among adolescents across the world. Second, we examined whether these associations differed by study site and sex. Methods Cross-sectional data from the IPEN Adolescent study, an observational multi-country study, were used. Participants wore an accelerometer for seven days, reported height and weight, and completed a socio-demographic survey. In total, 4852 adolescents (46.6% boys), aged 11–19 years (mean age = 14.6, SD = 1.7 years) were included in the analyses, using generalized additive mixed models. Results Adolescents accumulated on average 41.3 (SD = 22.6) min/day of MVPA and 531.8 (SD = 81.1) min/day of ST, and the prevalence of overweight and obesity was 17.2% (IOTF), but these mean values differed by country. Linear negative associations of accelerometer-based MVPA and ST with standardized BMI scores and the likelihood of being overweight/obese were found. School-based ST and non-school-based MVPA were more strongly negatively associated to the outcomes than non-school based ST and school-based MVPA. Study site moderated the associations; adolescent sex did not. No curvilinear associations were found. Conclusions This multi-country study confirmed the importance of MVPA as a potential protective factor against overweight/obesity in adolescents. Non-school-based MVPA seemed to be the main driver of these associations. Unexpected results were found for ST, calling for further examination in methodologically sound international studies but using inclinometers or pressure sensors to provide more precise ST measures.
The human visual system is able to adapt to a wide range of the adaptive luminance levels. However, the chroma was found to be the most affected attribute in the assessments. Several color appearance models have been proposed to describe adaptation mechanisms and predict the color appearance at different luminance levels. A set of 72 color pairs of samples that surround four color centers with high chroma was prepared to the test the prediction performance of the CAMs. The visual assessment of these color pairs was performed at eight luminance levels including photopic, mesopic and scotopic luminance levels. The data from visual assessment were used to the test prediction performance of six color difference formula and color appearance models, namely CIELAB, CIECAM02, CAM02-UCS, CAM16, CAM16-UCS and CAM16-UCS with power function.
The article describes the remediation of contaminated groundwater during the ex situ remediation of coal tar contamination following the closure of a coking plant in the Moravian–Silesian Region (Czech Republic). The aim of the article is to point out the advantages of ex situ soil remediation via the excavation of the contaminated geological environment combined with thermal desorption, a method of removing contaminants both from soil and groundwater. Its advantage is the absolute qualitative and quantitative control over the contaminated soil with the possibility of precise segmentation into contaminated and non-contaminated soils. Next, all contaminated groundwater may be pumped off upon the construction of sealing walls to control groundwater flows. To excavate the soil, it is necessary to reduce the contaminated groundwater level inside the sealing walls and thus create conditions for the extraction of contaminated soils using standard machinery. In detail, the article describes the removal of the contaminated groundwater and compares the quality of the pumped and inflowing water before and after the remediation. The locality is characteristic of a high horizontal and vertical grain-size heterogeneity of gravel-sand, which led to a varying filtration coefficient affecting the capacities of pumped groundwater quantity during the remediation. At the start of the remediation process, the contaminant levels exceeded the limits by the Czech Environmental Inspectorate several times. The post-remediation monitoring showed that all the contaminant levels were below the limit. Surprisingly, the overall groundwater contamination amounted to 232.86 t of contaminants as non-aqueous phase liquids, and 6872.9 kg of dissolved contaminants. As much as 12,200 t of contaminants were removed from the soil.
In the fabric industry, textile yarns are the fundamental building blocks. Hence, visualizing and studying yarn structure is essential to understand the structure and behavior of the fibers. Obtaining the yarn’s cross-section images is crucial in the calculations of yarn’s porosity; furthermore, a more precise expansion for the fiber’s migration can be concluded from the cross-sectional images. In this paper, three different methods (microtome, micro-computed tomography, and epoxy grinding–polishing methods) to image and visualize the yarn’s cross-section are presented. The experimental techniques are compared in terms of result useability, time of preparation, and overall outcome of the cross-sectional image. The images can be used for fiber distribution, air gap calculation, and twist analysis as well. The fiber diameter distribution of polyester yarn was measured based on the images obtained by the three different methods; the average fiber diameter measured based on the combined data from the three different methods was found to be 10.90 ± 0.30 µm.
A novel creep testing machine was designed to test austenitic steel foil AISI 347 under the elevated temperature of 700°C. The creep test was repeated in five stress levels from low‐stress 55 MPa to severe applied stress 220 MPa for 0.25 mm thickness samples. The machine was equipped with a shield inert gas injection system, and tests were repeated in a nonoxidative area. The creep rupture behavior of the foil is well represented using the modified three‐parameter Theta Projection Concept model. Each model parameter is best represented as a function of the applied stress. Comparison between the results of creep life in different mediums shows that the oxidation effect was the dominant phenomenon in the creep process. Moreover, avoiding oxidation affects the steady‐state stage growth, and afterward, the creep life was increased by more than 40%. Post analyses of ruptured creep samples compare the creep cavitation at triple grain boundaries in a different environment. Novel testing machine and method to measure the creep deformation of metal foils. Creep behavior of AISI 347 steel foil under various stresses at laboratory air and in argon environments. The use of shielding inert gas and its capability to protect the foil surfaces from oxidation. Stablish relationship between the creep life and axial creep conditions using modified theta projection concept.
High-strength steels are used more than general structural steel due to their combination of properties such as high strength, good toughness and weldability. They are mainly used in the manufacture of heavy vehicles for the mining industry, cranes, transportation, etc. However, welding these grades of steel brings new challenges. Also, a simulation for welding high-strength steel is required more often. To insert a material database into the simulation program, it is necessary to conduct investigations using CCT (Continuous Cooling Transformation) diagrams, welded joints research, and more. To investigate the behavior of S960MC steel during heating and cooling, we used dilatometry analysis supported by EBSD (Electron Backscatter Diffraction) analysis. A CCT diagram was constructed. The transformation temperatures of Ac1 and Ac3 increase with increasing heating rate. The Ac1 temperature increased by 54 °C and the Ac3 temperatures by 24 °C as the heating rate increased from 0.1 °C/s to 250 °C/s. The austenite decomposition temperatures have a decreasing trend in the cooling phase with increasing cooling rate. As the cooling rate changes from 0.03 °C/s to 100 °C/s, the initial transformation temperature drops from 813 °C to 465 °C. An increase in the cooling rate means a higher proportion of bainite and martensite. At the same time, the hardness increases from 119 HV10 to 362 HV10.
Detection of hazardous environmental pollutants to maintain safety is a significant concern worldwide. In this work, we developed a reliable and sensitive electrochemical sensor for the effective detection of a priority toxic pollutant, 4-nitrophenol (4NP), in the aquatic environment. A ternary nanocomposite was sonochemically prepared by anchoring silver nanoparticles doped rhombic dodecahedral zeolitic imidazolate framework-67 (ZIF-67) on reduced graphene oxide (RGO) nanosheets. We employed a solvothermal method in the preparation of ZIF-67, and the graphene oxide prepared by the Hummer’s method was chemically reduced using ascorbic acid. Important characterization techniques including XRD, SEM, elemental mapping, TEM, XPS, BET, Raman spectroscopy, FTIR, and EIS were used for evaluating properties of the synthesized nanomaterials. The prepared porous ternary nanocomposite evinced outstanding electrocatalytic activity towards 4NP determination, and the developed 4NP sensor showcased a very low detection limit of 0.3 nM and high sensitivity of 65.49 μAμM⁻¹cm⁻². Furthermore, significant performance criterions, including stability, reproducibility, anti-interference, and repeatability were examined to prove the reliability of the proposed sensor in 4NP quantification. The practical feasibility of the developed 4NP sensor was also evaluated by carrying out experiments with river water, lake water, and underground water samples.
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2,009 members
Jiri Chvojka
  • Department of Nonwovens and Nanofibrous Materials
Jiri Militky
  • Material Engineering
Kamil Zagorsek
  • Department of Geography
Jaroslav Vávra
  • Department of Geography
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Studentská 1402/2, 461 17, Liberec, Czechia
Head of institution
doc. RNDr. Miroslav Brzezina, CSc.
Website
www.tul.cz
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+420 485 353 612