Tomas Bata University in Zlín
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PVDF/PVDF-TRFE blends loaded with BaTiO3: from processing to performance testing
Get PDFConcerns surrounding the limited supply of fossil fuels have been the subject of much debate. As of promising solutions, polymers like poly(vinylidene fluoride) (PVDF) have gained attention due to their ability to generate electrical energy from the waste mechanical vibrations. The energy harvesting and vibration sensing potential of PVDF is however limited due to its low content of electroactive β-phase, which has to be increased by indirect post-processing. Recently, a synergistic effect was found in PVDF directly blended with its trifluoroethylene copolymer (PVDF-TrFE) due to strong interfacial polarization. In this study, we aim to further increment the piezoelectric performance of PVDF/PVDF-TrFE blends by incorporating a small amount of BaTiO3 nanocrystals via a facile and scalable processing route. The β-phase content was monitored using FTIR and XRD. Melt rheology experiments showed that co-blending of PVDF-TrFE as well as the addition of BaTiO3 slightly increased melt viscosity and complex modulus. Despite that, rheological data suggested that developed formulations can be processed by conventional techniques intended for a large-scale production. More importantly, PVDF/PVDF-TrFE binary blends supplemented with BaTiO3 are expected to exhibit superior d33 compared to conventional neat blends, which could make them highly promising for modern energy harvesting and sensor-related applications. © 2021 NANOCON Conference Proceedings - International Conference on Nanomaterials. All rights reserved.RP/CPS/2020/003, RP/CPS/2020/006; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Grantová Agentura České Republiky, GA ČR: 19-17457
Biodegradable films of PLA/PPC and curcumin as packaging materials and smart indicators of food spoilage
Get PDFBio-based and biodegradable packaging combined with chemical sensors and indicators has attracted great attention as they can provide protection combined with information on the actual freshness of foodstuffs. In this study, we present an effective, biodegradable, mostly bio-sourced material ideal for sustainable packaging that can also be used as a smart indicator of ammonia (NH3) vapor and food spoilage. The developed material comprises a blend of poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) loaded with curcumin (CCM), which is fabricated via the scalable techniques of melt extrusion and compression molding. Due to the structural similarity of PLA and PPC, they exhibited good compatibility and formed hydrogen bonds within their blends, as proven by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis confirmed that the blends were thermally stable at the used processing temperature (180 degrees C) with minimal crystallinity. The rheological and mechanical properties of the PLA/PPC blends were easily tuned by changing the ratio of the biopolymers. Supplementing the PLA/PCC samples with CCM resulted in efficient absorption of UV radiation, yet the transparency of the films was preserved (T-700 similar to 68-84%). The investigation of CCM extract in ethanol with the DPPH. assay demonstrated that the samples could also provide effective antioxidant action, due to the tunable release of the CCM. Analyses for water vapor and oxygen permeability showed that the PPC improved the barrier properties of the PLA/PPC blends, while the presence of CCM did not hinder barrier performance. The capacity for real-time detection of NH3 vapor was quantified using the CIELab color space analysis. A change in color of the sample from a yellowish shade to red was observed by the naked eye. Finally, a film of PLA/PPC/CCM was successfully applied as a sticker indicator to monitor the spoilage of shrimps over time, demonstrating an evident color change from yellow to light orange, particularly for the PPC-containing blend. The developed system, therefore, has the potential to serve as a cost-effective, easy-to-use, nondestructive, smart indicator for food packaging, as well as a means for NH3 gas monitoring in industrial and environmental applications.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMTMinistry of Education, Youth and Sports of the Czech Republic [RP/CPS/2020/006, RP/CPS/2022/007
The issue of homeless young people
Get PDFThis paper is devoted to the issue of homeless young people. At present, homelessness is a global problem with an increasing number of young people, who got on the street for various reasons. Homelessness itself can be understood as a complex generalized social failure of an individual. It is a social category of people who are clearly poor, living on the margins of society and characterized by their specific way of life, which puts them on the margins of society on the basis of their inability to participate in the quality of life and disrespect for the requirements of the majority society. The aim of the article is to present issues related to the phenomenon of homeless young people and understand the reasons and causes of their social degradation which led to their unfavorable social situation. Only appropriately applied social work can stop or reduce the number of young people living on the streets, and help them successfully reintegrate into the majority society
Spinel ferrite and MXene-based magnetic novel nanocomposites: an innovative high-performance electromagnetic interference shielding and microwave absorber
No full textAn ideal electromagnetic interference shielding and microwave absorber material should have dielectric and magnetic loss capabilities including good impedance matching, which can induce attenuation and absorption of incident electromagnetic waves. In this article, we have systematically reviewed recent advances on spinel ferrite and MXene-based innovative novel nanocomposites for electromagnetic interference shielding and microwave absorption application. The article covers MXene-spinel ferrite composite, MXene-spinel ferrite-carbon/graphene ternary composite, and MXene-spinel ferrite-polymer composite including a brief discussion on the basics of electromagnetic interference shielding and microwave absorption. Development strategies of nanocomposites with various components are also discussed. The challenges and future prospects of MXene and spinel ferrite-based nanocomposites are also proposed, which will pave the way to design an innovative next-generation outstanding electromagnetic wave absorber.RP/CPS/2022/007; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Grantová Agentura České Republiky, GA ČR: GA19-23647S; Univerzita Tomáše Bati ve ZlíněCzech Science Foundation project at the Centre of Polymer Systems, Tomas Bata University in Zlin, Czech Republic [GA19-23647S]; Ministry of Education, Youth, and Sports of the Czech Republic - DKRVO [RP/CPS/2022/007
Transformation of cellulose via two-step carbonization to conducting carbonaceous particles and their outstanding electrorheological performance
Get PDFIn this study, cellulose was carbonized in two-steps using hydrothermal and thermal carbonization in sequence, leading to a novel carbonaceous material prepared from a renewable source using a sustainable method without any chemicals and, moreover, giving high yields after a treatment at 600 degrees C in an inert atmosphere. During this treatment, cellulose was transformed to uniform microspheres with increased specific surface area and, more importantly, conductivity increased by about 7 orders of magnitude. The successful transition of cellulose to conducting carbonaceous microspheres was confirmed through SEM, FTIR, X-ray diffraction and Raman spectroscopy. Prepared samples were further used as a dispersed phase in electrorheological fluids, exhibiting outstanding electrorheological effects with yield stress over 100 Pa at an electric field strength 1.5 kV mm(-1) and a particle concentration of only 5 wt%, significantly overcoming recent state-of-the-art findings. Impedance spectroscopy analysis showed clear interfacial polarization of this ER fluid with high dielectric relaxation strength and short relaxation time, which corresponded to increased conductivity of the particles when compared to pure cellulose. These novel carbonaceous particles prepared from renewable cellulose have further potential to be utilized in many other applications that demand conducting carbonaceous structures with high specific surface area (adsorption, catalyst, filtration, energy storage).RP/CPS/2022/003; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMTMinistry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2022/003
Hepatocellular carcinoma versus nonalcoholic fatty liver disease: metabolic, environmental, and genetic association? De facto?
Get PDFNational Natural Science Foundation of China, NSFC: 61805222University Hospital Ostrava in the Czech Republic [MZ CR - RVO-FNOs/2019
Hierarchical MoS2/C@MXene composite as an anode for high-performance lithium-ion capacitors
Get PDFThe battery-type anodes and capacitor-type cathodes enable lithium-ion capacitors (LICs) to achieve high energy density and high power density concurrently. Nonetheless, the gap in capacity and electrochemical reaction dynamics between anodes and cathodes remains a grand challenge. In this work, we report the synthesis of hierarchical MoS2/C@MXene composite with uniform MoS2/C nanosheets grown on few MXene flakes by electrostatic flocculation and hydrothermal reaction. As a result, the restacking of MXene flakes is inhibited effectively by electrostatic flocculation, and the few-layer MXene provides abundant sites for the uniform growth of MoS2 nanosheets. Meanwhile, the amorphous carbon matrix derived from diethylenetriamine can further enhance the conductivity of MoS2 and mitigate the oxidation of MXene. Due to the desirable coupling effect between MoS2/C and MXene conductive networks, MoS2/C@MXene electrode demonstrates superior Li storage capacity. It delivers a reversible capacity of 600 mAh g−1 at 1.0 A g−1 after 700 cycles, along with excellent rate performance. Moreover, the assembled LIC device using MoS2/C@MXene as anode and three-dimensional porous carbon as cathode exhibits a high energy density of 164.5 Wh kg−1 at the power density of 225 W kg−1, and an energy density of 53.1 Wh kg−1 even at a high power density of 11.3 kW kg−1, as well as good cycling stability with capacity retention of 77.2% after 5000 cycles at 1.0 A g−1. These results indicate that MoS2/C@MXene might be promising anode materials for high-performance LICs. © 2022 Elsevier B.V.LTT20005; National Natural Science Foundation of China, NSFC: 22075082; Science and Technology Commission of Shanghai Municipality, STCSM: 18520744400; National Key Research and Development Program of China, NKRDPC: 2016YFE0131200National Natural Science Foundation of China [22075082]; National Key R & D Program of China [2016YFE0131200]; Science and Technology Committee of Shanghai Municipality [18520744400]; Czech Ministry of Ed-ucation, Youth and Sports INTER-EXCELLENCE programme [LTT20005
Optimal location and operation of waste-to-energy plants when future waste composition is uncertain
Get PDFIn many countries, waste management is increasingly geared towards a circular economy, aiming for a sustainable society with less waste generation, fewer landfills, and a higher rate of recycling. Waste-to-Energy (WtE) plants, which convert waste into heat and energy, can contribute to the circular economy by utilizing types of waste that cannot be recycled. Due to the varying quality of sorting and socio-economic conditions in individual regions, the waste composition differs between regions and has an uncertain future development. Waste composition significantly affects the operation of WtE plants due to differences in energy potential. This paper supports strategic capacity planning for waste energy recovery by introducing a two-stage stochastic mixed-integer linear programming model that captures waste composition uncertainty through scenarios of possible future development. The results of the model provide insights into the economics of operation and identify important factors in the sustainability of the waste handling system. The model is demonstrated on an instance with six scenarios for waste management in the Czech Republic for the year 2030. The solution of the proposed model is to build 14 new WtE plants with a total capacity of 1970 kt in addition to the four existing plants with a capacity of 831 kt. The annual energy recovery capacity is expected to increase almost four times to satisfy EU directives that restrict waste landfilling.Czech Ministry of Education, Youth and Sports/EU Operational Programme Research, Development and Education [CZ.02.1.01/0.0/0.0/16_026/0008413]; Czech Science Foundation [GA 20-00091Y]CZ.02.1.01/0.0/0.0/16_026/0008413, GA 20-00091
Examination of differences in using marketing tools in the management of SMEs in the Visegrád group countries
Get PDFThe main aim of the study is to examine the differences in the use of the marketing tools in the management of small and medium-sized enterprises in the Visegrád Group (V4) countries. The research was carried out via questionnaires, which were distributed to small and medium-sized firms in 2020. We obtained 1585 observations, which comprised the answers of business owners and managers. Binary logistic regression was used to process the data. Currently, firms rarely use the classic tools of the marketing mix. These tools are used to a minimal extent in construction and services. Proactive tools of the marketing mix are mostly used in transportation and retailing, and the least in manufacturing, construction, tourism, and other areas of business. Online marketing tools are mostly used in retailing, tourism, and services, and are less used in agriculture, construction, and transportation. The analysis results confirmed the differences in using the marketing mix tools depending on the age of the firm, the age of managers vs. entrepreneurs, and gender. The study results provide valuable information for creators of marketing conceptions, and for creators of regional and national development strategies. Similarly, these results encourage the creation of new marketing concepts and methodologies to evaluate their economic effects on firms and society. © 2022. The Author(s).1/0590/2
Towards improving the efficiency of software development effort estimation via clustering analysis
Get PDFIntroduction: The precise estimation of software effort is a significant difficulty that project managers encounter during software development. Inaccurate forecasting leads to either overestimating or underestimating software effort, which can be detrimental for stakeholders. The International Function Point Users Group's Function Point Analysis (FPA) method is one of the most critical methods for software effort estimation. However, the practice of using the FPA method in the same fashion across all software areas needs to be reexamined.
Aim: We propose a model for evaluating the influence of data clustering on software development effort estimation and then finding the best clustering method. We call this model the effort estimation using machine learning applied to the clusters (EEAC) model.
Method: We cluster the dataset according to the clustering method and then apply the FPA and EEAC methods to these clusters for effort estimation. The clustering methods we use in this study include five categorical variable criteria (Development Platform, Industrial Sector, Language Type, Organization Type, and Relative Size) and the k-means clustering algorithm.
Results: The experimental results show that the estimation accuracy obtaining with clustering consistently outperforms the accuracy without clustering for both the FPA and EEAC methods. Significantly, using the FPA method, the average improvement rate from using clustering as opposed to non-clustered was highest at 58.06%, according to the RMSE. With the EEAC method, this number reached 65.53%. The Industry Sector categorical variable achieves the best accuracy estimation compared to the other clustering criteria and k-means clustering. The improvement in accuracy in terms of the RMSE when applying this criterion is 63.68% for the FPA method and 72.02% for the EEAC method.
Conclusion: Better results are obtained through dataset clustering compared to no clustering for both the FPA and EEAC methods. The Industry Sector is the most suitable clustering method among the tested clustering methods. AuthorFaculty of Applied Informatics, Tomas Bata University in Zlin [IGA/CebiaTech/2022/001, RVO/FAI/2021/002