Tomas Bata University in Zlín
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The effect of apparent density of sulfidic crosslink and their chemical nature on self-heat build-up in carbon black filled Natural Rubber under cyclic mechanical loading
No full textNatural rubber is a widely used elastomer for the preparation of cyclically mechanically loaded products such as tires, where it reduces self-heating behavior. From a material point of view, the degree of self-heating depends on the composition of the rubber compound. One of the parameters influencing the self-heating of rubber is the type of curing system, which leads to different crosslinking density. The crosslinking density value for carbon black filled rubbers is only apparent due to the its physical interactions present and is referred to as the apparent crosslinking density (aCLD).Therefore, this work focuses on investigating the effect of sulfur intermolecular network formation by conventional (CV), semi-efficient (SEV) and efficient (EV) curing systems on the temperature development of cyclically loaded rubber using an advanced test method to in-situ determine the heat build-up. Rubber samples based on different curing systems were prepared by varying the concentration of the accelerator N-Tertiarybutyl-2-benzothiazole sulfenamide (TBBS) at a constant concentration of sulfur (2.5 phr). Using basic mechanical tests, it was found that the stiffness and hardness of the rubber increased with increasing aCLD and decreasing proportion of poly-sulfide bonds, respectively. Furthermore, cyclic mechanical analysis showed that with increasing aCLD and parallel decrease in the proportion of poly-sulfide bonds, both the loss modulus (G'') and dissipated strain energy increased, which was also reflected in the values of the mechanical stress-induced self-heating gradient. From the values of maximum developed temperatures, it was evident that the group of material with CV curing system showed the lowest self-heat build-up.Ministry of Education, Youth and Sports of the Czech Republic; DKRVO, (RP/CPS/2022/006
Mitigating resource curse impact through implementing circular economy effective strategies
No full textThe main goal of the study is to investigate and to evaluate the selected indicators of the circular economy with a relation to the international trade in order to create the effective tools and policies in the circular economy system. This is supported by the three research questions comprising the issues of the circular economy regarding the import and the export of the resources. Firstly, the intra-union and extra-union import of the materials and their impact along with the resource curse effects. The relations between the both import types and the circular material use rate are confirmed through a majority of the appropriate research hypotheses. Secondly, the resource curse negative impacts caused by the import and the export of the circular economy materials. The international trade brings the resources movements that would be not possible without it. Almost all the assigned research hypotheses confirm that the mentioned impacts are mitigated by these movements. Thirdly, the influence of the import and the export of the materials on the circular material use rate regarding the waste sort recycling rates. An influence of the international trade is occurred in the recovery rate that represents an outcome of recycling rate. Each research hypothesis is assigned to the particular explored indicator. Altogether, there are the 21 indicators examined in the regression analysis. Many relations regarding the statistical significance of the regressor are found. The testing phase follows after the regression model outcome. The discussion section demonstrates the implications arising from the analytical outcomes with a potential of altering the current policies in the circular economy system and the creation of the new ones in order to more efficiently use the available resources. The study outcome represents a valuable platform for potential construction of the effective policies and strategies necessary for implementing transition of the economies within the circular economy framework.Scientific Grant Agency of the Ministry of Education , Science, Research, and Sport of the Slovak Republic; Scientific Grant Agency of the Ministry of Education, Science, Research, and Sport of the Slovak Republic; Slovak Academy Sciences, (VEGA 1/0590/22)Scientific Grant Agency of the Ministry of Education, Science, Research, and Sport of the Slovak Republic; Slovak Academy Sciences [VEGA 1/0590/22
An experimental study on the effect of CO2 laser powers on melting characteristics of clear ice − part I: Horizontal irradiation
No full textIcing phenomenon widely exists in traffic and industrial fields, and causes a lot of safety accidents. Laser deicing technology is a typical high-efficiency and non-contact deicing method. To accurately predict and control the laser-induced ice melting process, an experimental study on melting characteristics of clear ice under horizontal CO2 laser irradiation and natural convection is carried out, with the laser power varied at a range of 20 ∼ 60 W. As resulted, in the first 27 s of the melting process, the axial melting rate is around 1.2 mm/s at each power. After 27 s, the laser power effect on the melting rate is obviously different, and the maximum melting rate reaches 5.41 mm/s at 50 W. The higher the laser power, the more the ice melts, and the easier the path of melting ice deflects. At 20 W and 50 W, the maximum angles of melting height are 1.14° and 4.18°, respectively. The laser power effect on the maximum melting height is obvious. At 20 W and 50 W, the peaks of maximum melting height are 12.84 mm and 22.59 mm, respectively. The higher the laser power, the larger the volume melting rate of ice, but the greater the energy loss, and it directly influences the energy efficiency. The ice-melting energy efficiency decreases with the increase of laser power. For laser at 20 W and 60 W, the maximum energy efficiency are 81.5 % and 54.6 %, respectively. This study is meaningful for the optimization of laser deicing technology.National Research Foundation of Korea, NRF; Ministry of Science, ICT and Future Planning, MSIP; Beijing Association of Refrigeration; National Natural Science Foundation of China, NSFC, (52076013); Beijing Municipal Science and Technology Commission, Adminitrative Commission of Zhongguancun Science Park, (3212024); National Foreign Expert Project of China, (G2022178023L)National Natural Science Foundation of China [52076013]; Beijing Municipal Science & Technology Commission [3212024]; National Foreign Expert Project of China [G2022178023L]; Government of the Republic of Korea (Ministry of Science and ICT); National Research Foundation of Korea; China-South Korea Young Scientist Exchange Program; Beijing Association of Refrigeratio
Quantification of shape parameters of Co-Cr-Mo-Si multiphase compounds and their role in the processing of metal injection molding feedstocks
No full textParticle shape is one of the most important powder attributes affecting the properties of multiphase compounds intended for metal injection molding. This work reports the processability of gas (GA) and water (WA) atomized Co-Cr-Mo-Si alloy related to quantitative analyses of particle shape using a newly developed algorithm based on the Euclidean distance mapping, which results are compared with those of commercially available dynamic image analysis. Both methods reveal similar values for the parameters that quantify the shape of the powders, such as circularity, aspect ratio, and symmetry. The alloys were mixed with wax/high-density polyethylene (50/50 wt%) binder using a double sigma mixer to produce homogeneous feedstocks. The critical solid loading and flow performance corresponding to the differences in powder shapes were derived from the torque and capillary rheometers, respectively, to obtain the optimum molding parameters. A stable and repeatable viscosity was observed for the GA feedstock, whereas the compound containing WA was prone to phase separation during flow. The defect-free sintered specimens were examined by metallographic analysis; the GA powder compound could be sintered to a maximum of 99.2 % of the theoretical density, whereas the irregular WA powder reached a maximum of 98.8 % of the theoretical density, and the carbon residue was found to be higher for the GA feedstock. The GA samples had a significantly higher ultimate tensile strength owing to their larger symmetry, which resulted in a lower porosity and stress concentration.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; DKRVO, (RP/CPS/2022/003
Electrodermal activity in polygraph testing
No full textElectrodermal Activity (EDA) is considered one of the most informative physiological responses to emotional stress, providing extensive data. This research is dedicated to investigating the measurement of EDA within the context of polygraph testing, utilizing the specialized LXSoftware. It includes a comprehensive analysis of EDA signal, with a particular emphasis on its correlation with various types of polygraph questions. Additionally, the study examines the characteristics of the EDA signal and factors that may potentially influence the measurements.Internal Grant Agency of Tomas Bata University in Zlin; Department of Security Engineering, Faculty of Applied Informatics, (IGA/FAI/2023/003
Study into the fire and explosion characteristics of polymer powders used in engineering production technologies
Get PDFPolymers and their processing by engineering production technologies (injection, molding or additive manufacturing) are increasingly being used. Polymers used in engineering production technologies are constantly being developed and their properties are being improved. Granulometry, X-ray, FTIR and TGA were used to characterize polymer samples. Determination of the fire parameters of powder samples of polyamide (PA) 12, polypropylene, and ultra-high molecular weight (UHMW) polyethylene is the subject of the current article. An explosive atmosphere can be created by the powder form of these polymer materials, and introduction of preventive safeguards to ensure safety is required for their use. Although the fire parameters of these basic types of polymers are available in databases (e.g., GESTIS-DustEx), our results showed that one of the samples used (polypropylene) was not flammable and thus is safe for use in terms of explosiveness. Two samples were flammable and explosive. The lower explosive limit was 30 g·m−3 (PA12) and 60 g·m−3 (UHMW polyethylene). The maximum explosion pressure of the samples was 6.47 (UHMW polyethylene) and 6.76 bar (PA12). The explosion constant, Kst, of the samples was 116.6 bar·m·s−1 (PA12) and 97.1 bar·m·s−1 (UHMW polyethylene). Therefore, when using polymers in production technologies, it is necessary to know their fire parameters, and to design effective explosion prevention (e.g., ventilation, explosive-proof material, etc.) measures for flammable and explosive polymers.Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky, (020STU-4/2021); Agentúra na Podporu Výskumu a Vývoja, APVV, (APVV-21-0187)Cultural and Educational Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republi
Correlations between the dopant concentration and ion transport properties of plasticized NaCMC-Pectin polyblend electrolyte membranes for electrochemical device applications
No full textThis study explores the structural and electrical properties of sodium carboxymethyl cellulose (NaCMC)–pectin (PC)–glycerol–NH4Br electrolyte films and investigates their potential applications in proton batteries. Plasticized solid polymer electrolyte (SPEs) films were fabricated using the solution casting method. The interaction between the salt and polymer blends was verified using Fourier-transform infrared (FTIR) analysis. Incorporation of various salt concentrations (up to 25 wt%) was found to enhance the amorphous phase of the polymer blend, as evidenced by X-ray diffraction (XRD) results. Additionally, the decrease in the glass transition temperature, as confirmed by DSC analysis, indicates that the inclusion of both plasticizer and salt contributed to this effect. An electrolyte with 25% wt. of NH4Br has the highest room temperature conductivity of 4.68 ×10−4 S cm−1. This electrolyte was employed to fabricate the proton battery for energy storage application.Internal Grant Agency of TBU in Zlin, (IGA/CPS/2023/002); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (RP/CPS/2022/002)Ministry of Education, Youth, and Sports of the Czech Republic [RP/CPS/2022/002]; In- ternal Grant Agency of TBU in Zlin [IGA/CPS/2023/002
The mediating role of auditing in created shared value optimization through Big Data analytics: A conceptual review
No full textThe essence of big data and big data analytics as technological breakthroughs is to create and share value among stakeholders. Numerous studies focus on the impact of big data analytics upon firm’s performance, big data analytics and auditing and big data with created shared value. There is very little if any study on the mediating role of auditing in the relationship between big data analytics and shared value optimization. As a methodology, we used ‘Publish or Perish’ which is an academic “search engine” to search all the articles on the big data analytics and firm performance; big data analytics and auditing; big data analytics and shared value optimization topics available on Crossref without time limit. Initial search generated 1000 studies as articles, books and other publications. Based on our criteria, we included only 32 articles focusing on big data analytics and auditing (n = 18); big data analytics and created shared value (n = 14); and, without big data analytics and firm performance (n = 18) already substantially covered in extant literature. The main finding is that there is no study to our knowledge and study’s limitation on the mediating role of auditing in the tripartite relationship following our conceptual model based on optimization theory of engineering and given the importance of information integrity for stakeholders
Cyberterrorism and social engineering - Methods and countermeasures
No full textThe article deals with the topic of cyberterrorism committed with the help of social engineering. It lists the means and methods used by modern cyber-terrorists but mentions in more detail the less common ones, which have a greater chance of success because they are not widely known. In the case of cyber terrorism or cyber war, the damage can become global. It is in the existential interest of every state or company to have a sufficient level of prevention against threats to its digital space and adequate settings of functional countermeasures. The article mentions these current countermeasures, especially the selected ones that correspond to the results of the SWOT analysis presented here. The topics of cybercrime include criminally punishable harmful behavior on the Internet such as Internet piracy (making illegal copies, illegal Peer-to-Peer file sharing, violation of copyright or industrial rights), dissemination of harmful content, a serious form of cyberbullying, cyber grooming, and cyberstalking. At present, especially the enormously increasing sophisticated organized crime, identity theft, or cyber-terrorism. From a general introduction to a better understanding of the topic, it goes on to a detailed description of individual current methods and focuses on the most frequently used techniques and methods of today like Watering Hole Attack, Cryptojacking, Pivoting, Credential Stuffing Attack, Website Defacement and Formjacking for example. In particular, social engineering methods, DDoS attacks, and password-cracking methods are described. Using an overview SWOT analysis, the article points out strengths and weaknesses, threats and opportunities concerning the currently most used methods of criminals. In conclusion, it presents the current requirements and measures, due to the constantly more sophisticated methods of modern attacks, for a secure organization and offers recommended procedures.Institute of Safety Engineering, Faculty of Applied Informatics; Univerzita Tomáše Bati ve Zlíně, UTB, (IGA / FAI / 2023/004
Comprehensive biodegradation analysis of chemically modified poly(3-hydroxybutyrate) materials with different crystal structures
Get PDFThis work presents a comprehensive analysis of the biodegradation of polyhydroxybutyrate (PHB) and chemically modified PHB with different chemical and crystal structures in a soil environment. A polymer modification reaction was performed during preparation of the chemically modified PHB films, utilizing 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane as a free-radical initiator and maleic anhydride. Films of neat PHB and chemically modified PHB were prepared by extrusion and thermocompression. The biological agent employed was natural mixed microflora in the form of garden soil. The course and extent of biodegradation of the films was investigated by applying various techniques, as follows: a respirometry test to determine the production of carbon dioxide through microbial degradation; scanning electron microscopy (SEM); optical microscopy; fluorescence microscopy; differential scanning calorimetry (DSC); and X-ray diffraction (XRD). Next-generation sequencing was carried out to study the microbial community involved in biodegradation of the films. Findings from the respirometry test indicated that biodegradation of the extruded and chemically modified PHB followed a multistage (2-3) course, which varied according to the spatial distribution of amorphous and crystalline regions and their spherulitic morphology. SEM and polarized optical microscopy (POM) confirmed that the rate of biodegradation depended on the availability of the amorphous phase in the interspherulitic region and the width of the interlamellar region in the first stage, while dependence on the size of spherulites and thickness of spherulitic lamellae was evident in the second stage. X-ray diffraction revealed that orthorhombic α-form crystals with helical chain conformation degraded concurrently with β-form crystals with planar zigzag conformation. The nucleation of PHB crystals after 90 days of biodegradation was identified by DSC and POM, a phenomenon which impeded biodegradation. Fluorescence microscopy evidenced that the crystal structure of PHB affected the physiological behavior of soil microorganisms in contact with the surfaces of the films.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Horizon 2020, (862910); Univerzita Tomáše Bati ve Zlíně, UTB, (IGA/FT/2022/006, IGA/FT/2023/002)European Union's Horizon 2020 Research and Innovation Program [862910]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/FT/2023/002, IGA/FT/2022/006]; Ministry of Education, Youth and Sports of the Czech Republic [90254