Tomas Bata University in Zlín
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Electromagnetic absorption characteristics of manganese-zinc ferrite and multiwalled carbon nanotube-filled composites based on NBR
No full textComposites based on acrylonitrile-butadiene rubber, carbon nanotubes, and manganese-zinc ferrite were fabricated and tested for electromagnetic interference (EMI) absorption shielding. First, carbon nanotubes and ferrite were solely used for the preparation of rubber composites. Then, carbon nanotubes were combined with magnetic filler and incorporated into the rubber matrix. The results revealed that carbon nanotubes act as reinforcing filler and significantly enhance the physical-mechanical properties of composites. The presence of carbon nanotubes in the rubber matrix also results in an outstanding increase in electrical conductivity and permittivity of composite materials, as a consequence of which the EMI absorption shielding was poor in the tested frequency range of 1 MHz to 3 GHz. On the other hand, ferrite-filled composites are able to efficiently absorb electromagnetic radiation emitted from various electronic and radiation sources. However, the tensile strength of the composites showed a decreasing trend with increasing content of ferrite. The combination of carbon nanotubes with manganese-zinc ferrite resulted in an improvement in the physical-mechanical properties of hybrid composites. As the permittivity of hybrid composites was still much higher in comparison with those filled only with ferrite, only the composite filled with 5 phr of carbon nanotubes and 100 phr of ferrite showed a slight EMI absorption shielding ability over the tested frequency range.Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-19-009
Innovative investigation of zinc oxide nanoparticles used in dentistry
Get PDFDental caries is a major lifestyle concern as dental components affect the face of an individual. The issue of tooth decay occurs in every age group throughout the globe. Researchers are probing incipient implements and techniques to develop filling agents for decayed teeth. Zinc oxide (ZnO) powder is utilized mostly as a filling agent. Nanotechnology enhanced the efficiency of compounds of metal oxides utilized for dental caries. The present study aims to investigate the properties of ZnO nanoparticles (NPs) synthesized chemically (using ZnCl2 and NaOH) as well as biologically (using aqueous leaf extract of Murraya paniculata). The XRD patterns confirm that ZnO NPs have a hexagonal crystalline structure with particle sizes of 47 nm and 55 nm for chemically and biologically synthesized NPs, respectively. The FE-SEM data confirm the nanorod and spherical/cubical shape morphologies for the chemically and biologically synthesized ZnO NPs, respectively. FTIR data show the peaks between 4000 and 450 cm(-1) of the functional groups of -OH, C-O, -C-H-, and Zn-O bonds. The UV-Vis absorption study indicates a peak around 370 nm and a hump around 360 nm corresponding to the chemically and biologically synthesized ZnO NPs, respectively. An antibacterial bioassay was performed and compared with commercially available ZnO bulk powder against tooth decaying pathogens, viz., Streptococcus mutans, Staphylococcus aureus, E. coli, and Lactobacillus fermentum, and found that both ZnO NPs had results closer to those of the standard drug (rifampicin). Thus, the synthesized ZnO NPs may be utilized as nano-drugs for the application of tooth decaying filling agents. Even biologically synthesized ZnO NPs may be considered more environmentally friendly and less toxic to human health concerns.UGC, New DelhiUniversity Grants Commission, UGC; University of Lucknow, L
Conducting and magnetic hybrid polyaniline/nickel composites
Get PDFHybrid organic/inorganic polyaniline/nickel composites were prepared by the in-situ oxidation of aniline hydrochloride with ammonium peroxydisulfate in the presence of various portions of nickel microparticles. Electron microscopies demonstrated the coating of nickel with polyaniline. FTIR and Raman spectroscopies indicated the reduced degree of polyaniline protonation. As a consequence, the composites containing 7.2–58.8 wt% of nickel had the conductivity of the order of 10−3–10−2 S cm−1, i.e. several order of magnitude lower than the conductivity of polyaniline or nickel. The conductivity as a function of applied pressure is also reported. Relatively low conductivity of composites is explained by the partial reduction of polyaniline with hydrogen gas evolved during the synthesis and consequent hydrogenation of polyaniline catalysed by nickel. The accompanying partial dissolution of nickel manifests itself by the reduced composite yield. The reason why hydrogen is generated mainly after the synthesis of polyaniline is discussed. The magnetic properties afforded by nickel are also reported. The composites dispersed in thermoplastic polyurethane matrix providing mechanical properties have been tested for electromagnetic interference shielding.RP/CPC/2020/005; Technology Agency of the Czech Republic, TACR: TH71020006, TK03030157; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Grantová Agentura České Republiky, GA ČR: 22-25734SMinistry of Education, Youth and Sports of the Czech Republic [DKRVO RP/CPC/2020/005]; Technology Agency of the Czech Republic [TH71020006, TK03030157]; Czech Science Foundation [22-25734S
Non-aqueous synthesis of homogeneous molybdenum silicate microspheres and their application as heterogeneous catalysts in olefin epoxidation and selective aniline oxidation
Get PDFIn this work, a novel synthesis of homogeneous molybdenum silicate spheres under non-aqueous conditions is presented. A preparation method is based on the condensation of molybdenum metal–organic framework-based precursor solution prepared via a microwave-assisted approach from bis(acetylacetonato)dioxomolybdenum and biphenyl-4,4′-dicarboxylic acid with 3-aminopropyltriethoxysilane under non-aqueous conditions. The as-prepared product was calcined at 500 °C to obtain amorphous and porous molybdenum silicate microspheres with homogeneously distributed molybdenum species within silicate matrix. The microspheres exhibit an average size of about 480 nm. This material was further studied as a heterogeneous catalyst for the epoxidation of olefins via the model catalytic epoxidation of cyclohexene with cumylhydroperoxide. High catalytic activity at the moderate temperature (65 °C) with the conversion of 86% after 2 h and the high selectivity to cyclohexene oxide has been achieved. In addition, molybdenum silicate microspheres exhibit catalytic activity and high selectivity in the oxidation of aniline to nitrosobenzene. © 2021 The Korean Society of Industrial and Engineering ChemistryRP/CPS/2020/006; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: LM2018110, LM2018127; Grantová Agentura České Republiky, GA ČR: GJ20-03636Y; Central European Institute of Technology, CEITEC; European Regional Development Fund, ERDF: CZ.1.05/2.1.00/19.040
Innovative relations within the software application for Industry 4.0
Get PDFThe article deals with the preparation and definition of new relations within a software tool aimed at increasing the efficiency of production processes. These are three types of innovative concepts: Digital Master, Digital Technologist and Digital Twin that can be provided to customers separately, but also as integration into existing software in the production and logistics management process. By defining these relations within the developed software tool and its implementation into the production process, the automation and digitization of logistics processes in production facilities will reach a higher level that meets the requirements of Industry 4.0.European Union [OPVaI-MH/DP/2018/1.2.2-17]; Department of Production Engineering of Tomas Bata University in Zlin; foundation of Ministry of education, science, research and sport of the Slovak Republic [KEGA 005TUKE-4/2021
The impact of intraday momentum on stock returns: Evidence from S&P500 and CSI300
Get PDFThis paper analyzes the statistical impact of COVID-19 on the S&P500 and the CSI300 intraday momentum. This study employs an empirical method, that is, the intraday momentum method used in this research. Also, the predictability of timing conditional strategies is also used here to predict the intraday momentum of stock returns. In addition, this study aims to estimate and forecast the coefficients in the stock market pandemic crisis through a robust standard error approach. The empirical findings indicate that the intraday market behavior an unusual balanced; the volatility and trading volume imbalance and the return trends are losing overwhelmingly. The consequence is that the first half-hour return will forecast the last half-hour return of the S&P500, but during the pandemic shock, the last half-hour of both stock markets will not have a significant impact on intraday momentum. Additionally, market timing strategy analysis is a significant factor in the stock market because it shows the perfect trading time, decides investment opportunities and which stocks will perform well on this day. Besides, we also found that when the volatility and volume of the S&P500 are both at a high level, the first half-hour has been a positive impact, while at the low level, the CSI300 has a negative impact on the last half-hour. In addition, this shows that the optimistic effect and positive outlook of the stockholders for the S&P500 is in the first half-hours after weekend on Monday morning because market open during the weekend holiday, and the mentality of every stockholder's indicate the positive impression of the stock market.program of the Minister of Science and Higher Education titled "Regional Initiativeof Excellence" in 2019-2022 [018/RID/2018/19]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [11631013, 11971372, 11801433]018/RID/2018/19, PLN 10,788,423.16; National Natural Science Foundation of China, NSFC: 11631013, 11801433, 1197137
Selected factors of internationalisation and their impact on the SME perception of the market risk
Get PDFResearch background: Internationalisation of entrepreneurial activities provides an ample opportunity for the growth and sustainability of small and medium-sized enterprises (SMEs). When making their business activities international, SMEs are facing various obstacles. Investigating the key factors of internationalisation and their impact on SME decision making constitutes a key factor of the research work. Purpose of the article: The main purpose of the paper is to examine the impact of selected factors of SME internationalisation on the positive perception of the market risk. Higher export costs. differences in legal environment, taxes. and linguistic and cultural differences were set to be the significant factors influencing the positive perception of the market risk. Bearing the main purpose in mind, the Visegrad Four (V4-Czech Republic, Slovakia, Poland, Hungary) were examined. Methods: The questionnaire in mother tongue of each country in online and paper form was used. The questionnaire consists of 77 questions divided into several sections. Likert five-point scale was used to allow the respondents to express their opinion. In total. 1585 responses were completed. A regression analysis was used to verify the statistical significance of the independent variables and to quantify the causal relationships (determining the direction and strength of the effect) on the dependent variable. As the variables are of one metric, a linear regression model (I,RM) was selected to validate the hypothesis. Findings & value added: The internationalisation of SME activities brings along many risks and barriers that SMEs need to overcome if they want to enter international markets. Many SMEs consider the barriers and restrictions to enter foreign markets to be severe. Therefore, they decide to do their business domestically. It was established in the research that only 30.2% of the respondents expanded their business activities internationally. The biggest impact on the positive assessment of the market risk was found to have linguistic and cultural differences. They do not have a negative effect on the positive perception of the market risk, so they do not hinder SMEs in their international expansion. The second most important was the factor of the export costs. The factor of possible increased costs is quite important for SMEs in making their decisions whether to expand internationally or not. This factor also shapes a positive approach to assessing the market risk by SMEs. In the research, SMEs confirmed that potential higher costs do not represent a major barrier for them in shaping their attitudes towards the market risk. The remaining factors being analysed. namely differences in legal environment and taxes. did not have a significant impact on the positive assessment of the market risk internationally. The practical implications can be found in new information about market risk in process of internationalisation provided from four selected countries.Ministry of education, science, research and sport of the Slovak Republic [1/0689/20]Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 1/0689/20; Kementerian Pendidikan Malaysia, KP
Organizational diversity and competency-based performance: The mediating role of employee commitment and job satisfaction
Get PDFDiversity amongst the workforce within central Europe has experienced some form of evolution. This occurrence will incessantly manifest even further in the not-too-distant future. As a result, citizen-dominated societies are gradually tilting towards an increasingly diverse and minority population, broadly of African and Asian descent. Again, demographers suggest the influx of women, minorities, people of different ethnic backgrounds, aging workers, and people with alternative lifestyles within the European employment space, just as the various organizations and schools are filled with these groups. Studies on organizational diversity abound, however, findings from past research on diversity and performance relationships have been equivocal. Thus, the main objective of this study is to assess the mediating role of commitment and job satisfaction in the relationship between diversity and performance. Results from 237 samples drawn from the Czech Republic, Europe and analyzed through partial least square structural equation modelling (PLS-SEM) suggest that diversity does not have a significant relationship with competency-based performance. However, both commitment and job satisfaction play notable roles in the relationship between diversity and competency-based performance. Given these results, we discuss the theoretical and managerial implications.Tomas Bata University in Zlin [IGA/FaME/2020/003]; Internal Grant Agency of the Faculty of Management and Economics at Tomas Bata University in Zlin, Czech Republic [IGA/FaME/2021/003
Effect of conditioning on PU foam matrix materials properties
Get PDFThis article deals with the characterization of the thermal-induced aging of soft polyurethane (PU) foams. There are studied thermal and mechanical properties by means of thermal analysis, tensile, compression and dynamic mechanical vibration testing. It was found in this study, that the increasing relative humidity of the surrounding atmosphere leads to the initiation of the degradation processes. This is reflected in the observed decreased mechanical stiffness. It is attributed to the plasticization of the PU foams wall material. It is in agreement with the observed increase of the permanent deformation accompanied simultaneously with the decrease of Young's modulus of elasticity. The latter phenomenon is studied by the novel non-destructive forced oscillations vibration-damping testing, which is confirmed by observed lower mechanical stiffness thus indicating the loss of the elasticity induced by samples conditioning. In parallel, observed decreasing of the matrix hardness is confirming the loss of elastic mechanical performance as well. The effect of conditioning leads to the significant loss of the PU foam's thermal stability.European Regional Development Fund in Research Centre of Advanced Mechatronic Systems project within Operational Programme Research, Development and Education [CZ.02.1.01/0.0/0.0/16_019/0000867]; Internal Grant of Palacky University in Olomouc [IGA_PrF_2021_031]CZ.02.1.01/0.0/0.0/16_019/0000867; Univerzita Palackého v Olomouci: IGA_PrF_2021_03
Effect of temperature ageing on injection molded high-density polyethylene parts modified by accelerated electrons
Get PDFThe temperature ageing of high-density polyethylene (HDPE) modified by accelerated electrons was studied. Commodity plastic HDPE was used as a basic polymer material which was modified by radiation cross-linking. This polymer was used because of its excellent processability and chemical resistance. Plastic injection molding technology was used for the production of test specimens. These specimens were modified with the dose of radiation 33, 66, 99, 132, 165, and 198 kGy. The prepared specimens were tested to determine: gel content, degree of swelling, temperature stability, and changes in mechanical properties after temperature ageing. The results were determined by scanning electron microscopy (SEM) analysis on the fracture surfaces. The results of this study confirm that modification of HDPE by radiation cross-linking has a significant effect on increasing temperature stability. It has been shown that HDPE modified by radiation cross-linking can withstand temperatures exceeding the melting point of the original HDPE for a short-term. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.LO1303, MSMT-7778/2014; European Regional Development Fund, ERDF: CZ.1.05/2.1.00/19.037